VWDiesel.net The IDI, TDI, and mTDI source.
General Information => General => Topic started by: VWRacer on June 21, 2004, 10:46:26 am
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Hey Jake!
There is a great thread over on the TDI Forum (click here (http://forums.tdiclub.com/showflat.php?Cat=&Number=768269&Main=768197#Post768269)), authored by TDIMeister, detailing the installation of an SDI intake manifold on his TDI.
Enjoy! :D
Stan
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Hey Jake!
There is a great thread over on the TDI Forum (click here (http://forums.tdiclub.com/showflat.php?Cat=&Number=768269&Main=768197#Post768269)), authored by TDIMeister, detailing the installation of an SDI intake manifold on his TDI.
Enjoy! :D
Stan
Sorry, should have cross-posted here too... :oops: :P
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Awesome - thanks for the note - looking forward to hearing an update after you get the quirks worked out, IE: how it changes the RPM powerband, and also hopefully some pictures. Got a measurement on the SDI manifold runner lengths?
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Got a measurement on the SDI manifold runner lengths?
By my estimation, darn close to 2 to 2-1/2 of my size 10 feet, including port length :lol:
Sorry, I didn't take any pics as I was real busy under the hood, but photos WERE taken by others and I'm eagerly awaiting to see them myself.
The manifold met my expectations of what I wanted it to do. Smoke out the tailpipe appears to be noticeably reduced at WOT, and steady cruise at 75 MPH has boost at 4.5 PSI when it used to be around 6 PSI. These two factors tell me the engine is getting more air mass flow overall without more boost through better volumetric efficiency. Nothing was done to fuelling rate, so no, seat-of-the-pants is not significantly different, nor was that ever expected. What this manifold HAS allowed is more fuelling without smoke.
A couple of unresolved, relatively minor issues were listed in the aforementioned link. I don't see much impeding these from being ironed-out in the very near future.
Cheers,
Dave
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Got a measurement on the SDI manifold runner lengths?
By my estimation, darn close to 2 to 2-1/2 of my size 10 feet, including port length :lol:
Sorry, I didn't take any pics as I was real busy under the hood, but photos WERE taken by others and I'm eagerly awaiting to see them myself.
The manifold met my expectations of what I wanted it to do. Smoke out the tailpipe appears to be noticeably reduced at WOT, and steady cruise at 75 MPH has boost at 4.5 PSI when it used to be around 6 PSI. These two factors tell me the engine is getting more air mass flow overall without more boost through better volumetric efficiency. Nothing was done to fuelling rate, so no, seat-of-the-pants is not significantly different, nor was that ever expected. What this manifold HAS allowed is more fuelling without smoke.
A couple of unresolved, relatively minor issues were listed in the aforementioned link. I don't see much impeding these from being ironed-out in the very near future.
Cheers,
Dave
Very good! So those long runners are now probably sucking the air right out of the turbo's compressor outlet? ;) The reduced boost pressure for constant cruise setting is a very encouraging sign indeed! What RPM do you cruise at 75 MPH at?
I was hoping for a total intake manifold runner length from head to plenum of about 2 feet. Sounds like this SDI manifold might be just the ticket!
I hope someone got some shots of it, I especially want to see how much room it leaves atop the injection pump. This is where I think the LDA device on an IDI motor might stick up a lot farther than a TDI injection pump.
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What RPM do you cruise at 75 MPH at?
Dr. Diesel will be REALLY jealous... :lol: :wink: 2550 RPM.
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Dr. Diesel will be REALLY jealous... 2550 RPM.
Heh heh - you have to love Passat and A3 TDIs for that. The gearing in my Jetta is silly tall. On a recent trip to Ottawa we were cruising at around 145km/h (~90mph) - and the tach was just north of 3k (3100ish IIRC.)
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Dr. Diesel will be REALLY jealous... 2550 RPM.
Heh heh - you have to love Passat and A3 TDIs for that. The gearing in my Jetta is silly tall. On a recent trip to Ottawa we were cruising at around 145km/h (~90mph) - and the tach was just north of 3k (3100ish IIRC.)
I'm stuck in Dr.D's world .... 3900 @ 120km/h
Redline at 147km/h
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I'm stuck in Dr.D's world .... 3900 @ 120km/h
Redline at 147km/h
Ouch. The Scirocco GTD has a 7A gearbox - .71 fifth on a 3.94 final drive - not quite as tall as an early FF with .71 fifth, but still pretty decent. I'm turning 3 grand at 120, and I run out of steam (and head gasket) at 175.
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What RPM do you cruise at 75 MPH at?
Dr. Diesel will be REALLY jealous... :lol: :wink: 2550 RPM.
Thanks for the info! It was on this thread in the old forum that I did some intake manifold runner length calculations (with Stan's help) applied to my 1.6lTD:
http://www.hostboard.com/cgi-bin/ultimatebb.cgi/ubb/get_topic/f/4037/t/683/p/2
A table I came up with from that thread:
air temp = 122 deg. F (1182.6 ft/s)
runner length: 23.0" 23.5" 24.0" 24.5" 25.0"
Tuned RPM RV=2 5683 5582 5484 5390 5299
Tuned RPM RV=3 3788 3721 3656 3593 3533
Tuned RPM RV=4 2841 2791 2742 2695 2650
air temp = 68 deg. F (1126 ft/s)
runner length: 23.0" 23.5" 24.0" 24.5" 25.0"
Tuned RPM RV=2 5413 5316 5223 5134 5047
Tuned RPM RV=3 3608 3544 3482 3422 3365
Tuned RPM RV=4 2706 2658 2612 2567 2524
Note that for runner length, I have already subtracted out the 4" runner length that is inside the head. So those are the runner lengths of just the intake manifold.
I can see the cam timing being a little bit different on the TDI than the 1.6lTD, and also there is a margin for error (theory may leave out a tangible effect for example wave speed might be different one direction vs the other in flowing gas) But anyway... at your 75mph cruise and 2550 RPM, I am guessing you are closest to the 4th reflected value peak. According to Stan (and you might know more about this too) the 3rd and 2nd RV are even more powerful than the 4th, and I would plan on being able to use the 2nd and 3rd RVs in addition to the 4th. So it is very encouraging to see you got such a tangible benefit at only the 4th RV! Can't wait to see what the 3rd RV is like from your testing at higher RPMs. :) I wouldn't expect your motor to be able to wind high enough to see the 2nd RV though.
My main goal is to beef up my motor's powerband in the the power band in the 2500-3200rpm area, which is before the turbo has fully kicked in making peak boost pressure, in order to broaden the usable RPM range of my motor down lower. Any benefits given by the 3rd and 2nd RV will be icing on the cake. ;)
FYI: Here is a G-tech plot of my motor's hp and torque curves, to give you a feel for what the power characteristic is like:
(http://www.imagestation.com/picture/sraid77/p308de5cd6daeafcbf28b813dbcb6c5f5/fb40086b.jpg)
Are you planning on doing any G-tech or dyno testing? Did you get any baseline results by chance?
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Got a measurement on the SDI manifold runner lengths?
By my estimation, darn close to 2 to 2-1/2 of my size 10 feet, including port length :lol:
If so, expanding on your estimation, the length of your feet is 10 2/3". (according to: http://www.boot.com/bsizcvt.htm#SizeTable ). That would put the total runner length at 21.33" to 26.66".
Assuming you mean including the length of the port inside the head? If so, and and assuming the length of the port inside the head is 4" in the TDI like I estimated in the 1.6l IDI head, that would give manifold runner length to head-manifold interface length of 17.33" to 22.66".
Hard to say with precision, but it's at least ballpark close to the 22-26" target that I am shooting for. (Yeah OK, could probably have told that just from looking at the pictures, I know... :o )
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I just noticed that there are pictures on the TDIForum thread showing this manifold installed now; nice.
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i still can't believe dave got it all buttoned up and drove it home that day!!! :lol:
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quote from TDIclub:
Is the blue "goop" along the seam of the plastic runners and plenum part of the factory piece or was it added to fix air leaks?
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i was checking that manifold out and i didnt notice the blue goop. fairly certain that was added to fill air leaks. (i was suspect of the unit holding boost..)
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What RPM do you cruise at 75 MPH at?
Dr. Diesel will be REALLY jealous... :lol: :wink: 2550 RPM.
Not for long!! Peloquin'd ASF tranny w/ 100mm flanges, 3.67 r&p, and .71 5th! Can't wait!
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i still can't believe dave got it all buttoned up and drove it home that day!!! :lol:
Hard to believe, but true :)
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quote from TDIclub:
Is the blue "goop" along the seam of the plastic runners and plenum part of the factory piece or was it added to fix air leaks?
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i was checking that manifold out and i didnt notice the blue goop. fairly certain that was added to fill air leaks. (i was suspect of the unit holding boost..)
No, it wasn't there originally, but the goop was applied just an experiment to trace IF there was a boost leak through the seams of the moulded manifold halves. There doesn't seem to be any... so I believe it's holding up under boost. I meet with Gerry again this weekend to see if we can put this one to bed.
In the final analysis, was it worth the $327 US? HP per dollar, no. I'd sooner install an FMIC or a modded pump, or bigger injectors, or an after market cam, or custom chiptuning. But I knew from the very outset that the HP gains from this manifold in and of itself would be negligable.
Jake, if you're looking for real gains in your ride, class rules permitting, I'd sooner adapt a VNT-turbo into your car and get a Giles pump. Can you put modded / bigger injectors into an IDI motor like you can on the TDIs?
Dave
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No, it wasn't there originally, but the goop was applied just an experiment to trace IF there was a boost leak through the seams of the moulded manifold halves. There doesn't seem to be any... so I believe it's holding up under boost. I meet with Gerry again this weekend to see if we can put this one to bed.
In the final analysis, was it worth the $327 US? HP per dollar, no. I'd sooner install an FMIC or a modded pump, or bigger injectors, or an after market cam, or custom chiptuning. But I knew from the very outset that the HP gains from this manifold in and of itself would be negligable.
Jake, if you're looking for real gains in your ride, class rules permitting, I'd sooner adapt a VNT-turbo into your car and get a Giles pump. Can you put modded / bigger injectors into an IDI motor like you can on the TDIs?
Um, really in a competitive race classing situation, the "real" gains are no longer available as they've already been done, assuming the rules are anywhere near fair! I am already pretty competitive at this point, and am just focusing on fine-tuning. IE: any honest-to-goodness 3% power gains that I can get without too much work, I don't want to leave on the table. So, I am focusing on what others might not consider to be real gains, although for me something like a 3-6% honest to goodness increase in peak horsepower is VERY noticeable and helpful on the track. If I can combine together a few small gains... they all work together and what do you know it, the overall system is getting FASTER.
My autocross racing class is actually quite restrictive, although that can be viewed as a good thing, for helping to somewhat keep a cap on the budget.
First and formost - this surprises most turbo-diesel folks: It doesn't allow any changes to wastegate or turbocharger. Engine internals must remain unmodified (only blueprinting within the factory specifications are allowed) and camshaft must also remain stock. The exhaust system is free, complete fuel injection system is free, intercooling is free, and also the manifolds (both exhaust and intake) are free. I have modified fairly extensively (of course not completely... but there are diminishing returns) all of the above with the exception of the manifolds, which I have only port-matched to the head (this is allowed up to 1" depth into the head), and I have ceramic-coated my exhaust manifold to maintain heat inside and through the turbine section to reduce turbo lag. I have an audi5000 intercooler that is highly efficient, and does not restrict boost pressure measurably, 2.5" exhaust system in combination of stainless and lightweight aluminum with a custom downpipe from the turbine outlet back and no muffler, 1.9lTD 2-stage injectors and have done some dyno testing with change the governor mechanism on my fuel injection pump, but the pump remains the stock plunger 9mm bore and stroke. It is at least close to being rich enough though! And it is costly going to a bigger or better pump setup (believe me, I am considering that.) About the only thing I haven't done besides extensive blueprinting work (who knows I may be going down that route soon, as I may have to build another motor to replace my old damaged one) is optimize the intake and exhaust manifolds. Since changing the exhaust manifold is more difficult and expensive than the intake, I was leaning towards keeping the stock exhaust manifold, and along with that not change the turbo mounting location, exhaust system from turbine back, turbo oil return, and air intake system. So I have high on my list of performance optimizations upcoming, replacing the factory intake manifold with a custom long-runner unit designed to optimize the usable power curve.
Sure, more max hp would be great if that were possible, but my car I think is powerful enough in my class, and it might be unrealistic to expect large power gains from a long-runner intake (something like a 3% power gain might be possible and would be VERY welcome, of course!) What I would hope to get though primarily with the long-runner intake manifold, is a broadening of the usable torque curve down lower into the RPM range, basically to make it so I can keep it in 3rd gear through slower turns without it lugging and making me shift to 2nd. Currently when the RPMs drop down to about 2500-3000rpm at speed in 3rd gear, the engine bogs as the turbo is not spooled up and engine needs to accelerate more before the turbo is working to a point where it comes "on-boost". I'm thinking a well-engineered custom long-runner intake manifold could help the turbo start working in this area where now the motor bogs, and thereby extend my usable RPM curve down lower into the RPM range. Sure, any benefits in HP up higher would be a nice side benefit, but that's not my primary goal. A 3% power gain on the side would be nice though and I will certainly take that if I can get it! OTOH, a significant restriction in mid or high-RPM airflow, or much power LOSS in that area, would be unacceptable. An objective with the long-runner intake manifold project would be to not see a significnat reduction in power at any are in the powerband. (down at idle, I don't care... up high in RPMs above the revv limiter, I don't care right now, although I may be experimenting with revving the engine higher as well, but that is another project.)
Maybe I should also point out that if my power curve were beefier down at a lower RPM, at the autocross school where my car broke, I may have been able to have left it in 3rd gear in the section that I had to run it in 2nd where I mis-shifted into 1st instead of 3rd, over-revving my motor and bending the valves. Yeah... you see it was the intake manifold that killed my motor!!! (OK, just kidding... but hopefully that does help to illustrate the need I have for broadening my power curve down lower... reduce or remove the need to shift! having to shift a lot in the middle of an autocross course is bad! There are enough other things for me, the driver to think about... course recall and looking ahead, where does the braking point start (can't left foot brake if you need to downshift at the same time!), where to position the car and turn in, what line to take, are all cones where they should be or should I stop if one's out of place from where I remember it should be on the coursewalk and point it out so I can get that re-run, etc. if I can remove the worry about "can I get through this corner in 3rd or am I going to have to downshift into 2nd to avoid a bog", etc... it's a good thing! Anyway, you get the picture.)
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TDIMeister
Have you noticed any measurable increase in fuel economy with the manifold?
fspGTD
Regarding your stock exhaust manifold, have you considered extrude honing? I don't know how much it would be, but at least you don't have to change the location of the turbo.
Peter
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Jake, IMHO you might consider looking to adapt a manifold from a non-cross-flow 2.0 gasser. It also has long runners (albeit no where as long as the SDI ones... much easier to find and likely much, much cheaper.
The SDI manifold will not stay in my car for long... I have visions of grandeur to build a complete motor incorporating this manifold and a VNT-20 turbo I just bought. This, and a RedRotors-modified pump, big honking injectors and custom programming will make this a Monster TDI! :)
Since intercooling and fuel injection mods are unlimited, exploit this to the fullest possible extent! Plumb a dual-IC setup ora massive unit that covers the entire front-end or something! :D What are the rules about changing turbos? IIRC is must be from a unit that was incorporated in the OEM engine, although you are able to go through the parts bin in case there were different, better units from different years? The old T3 turbos are relatively unresponsive, inefficient units. A GT-15 or KKK K03 would give a nice improvement in spool-up time and will have greater efficiencies. Both were used in later 1.9 IDIs.
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TDIMeister
Have you noticed any measurable increase in fuel economy with the manifold?
I'm right at about my average. My driving patterns are relatively consistent with about 75% of my kms put on the highway, and the rest on a short 9 km commute to/from work. I'm getting mid-5s L/100km. While I don't abuse my car, I don't exactly drive like a granny, either.
So, short answer is: No noticeable difference with the manifold.
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Jake, IMHO you might consider looking to adapt a manifold from a non-cross-flow 2.0 gasser. It also has long runners (albeit no where as long as the SDI ones... much easier to find and likely much, much cheaper.
Let's see... you mean like from an Audi 2.0l reverse-flow block? Like the other gasser reverse-flow blocks, my turbo sits too high and would interfere with it's layout. Now I would definitely try that if I were to change my exhaust manifold to relocate the turbo lower and out of the way, but that's a bigger project... re-doing the turbine outlet exhaust system, relocating the turbo, changing the oil return line, re-doing the air inlet tract going to the compressor inlet, not to mention boost tubing coming off the compressor outlet...
The SDI manifold will not stay in my car for long... I have visions of grandeur to build a complete motor incorporating this manifold and a VNT-20 turbo I just bought. This, and a RedRotors-modified pump, big honking injectors and custom programming will make this a Monster TDI! :)
Since intercooling and fuel injection mods are unlimited, exploit this to the fullest possible extent! Plumb a dual-IC setup ora massive unit that covers the entire front-end or something! :D What are the rules about changing turbos? IIRC is must be from a unit that was incorporated in the OEM engine, although you are able to go through the parts bin in case there were different, better units from different years?
With my current setup, intercooler efficiency of the single audi5k intercooler at stock peak boost pressure are very efficient, so little would be gained by adding another intercooler, and there would be the negative of added weight and volume in the intake tract that could actually decrease overall performance. Also, although intercooler are unrestricted, you can't just go cutting holes, etc and do unauthorized modification to get them to fit. You've got to carefully place them. Anyway based on test results of the intercooler outlet air temp as well as pressure loss through the intercooler, I think I am already near-optimal on the intercooling situation.
FYI: Here is the section of the rulebook that has most of the items that cover street prepared class:
http://mouton.best.vwh.net/sccasolo/Rules/sp.html
I can only update/backdate '75-'84 Rabbits and Jettas. That leaves as the only turbo diesel engine option, the '83-'84 engine code "CY" turbo-diesel 1.6l solid-lifter, for which there were 2 turbos available: a KKK and a Garrett, both of which came with the same peak boost pressure specs (9-10psi).
There are a few other interesting options I've considered, but they are not what most folks do to their street cars. Water injection is permitted (but no alcohol.) Also, CNG-fumigation is permitted. Like I said before, my car is pretty fast as is... I'm not in need of a huge power gain. Of course, if there is something big I've left on the table, I'd like to find what that is, but trust me I've given this a lot of thought and you can rule out upping the boost pressure (beyond maybe blueprinting the stock turbo to the upper limit of the specification, probably not more than 10psi).
Oh yeah, I do think there is a lot of potential to be had in the fuel injection. And this is an area I have been and will continue to focus a lot of research time on. I have seen HUGE power increases in this area already. (One of the main power boosters that allows me to kick out around approx 120hp on stock boost pressure out of a motor that originally had 68hp! Not to mention how much higher the power curve extends that the stock motor (whereas the stock governor petered out starting at around 4500rpm, I've gotten mine to pull with full power up to about 5500+rpm!)
Believe me, it's very good that I stay in this class. Were I to mod my turbo, I'd go into prepared class, where lightened cars trailered-only need apply, with lexan windows, stripped interiors, double a-arm conversions, fully-internally built motors, etc. Or street mod class, not much better. Street prepared is where I can hang with the 1.8l "JH" sciroccos, Rabbits and GTIs, etc. It's a good competitive class where VW drivers have taken national championships. Frankly I feel in current state of tune, my 1.6lTD was at least as competitive as a prepped to the limit 1.8l"JH" motor, so anything I can do to make it even better will only further the advantage! On the disadvantages of my setup, a 2-dr version would be approx 55lbs lighter than my 4-dr version. And a scirocco although not lighter than a Rabbit (actually a little heavier) may be more competitive yet, likely due to a lower center of gravity. There is a rule change proposal in the works by that way that would combine 8v sciroccos with the Rabbits/Jettas onto the same line... which would mean that an '83-'84 1.6lTD swapped into a scirocco would be legal!
The old T3 turbos are relatively unresponsive, inefficient units. A GT-15 or KKK K03 would give a nice improvement in spool-up time and will have greater efficiencies. Both were used in later 1.9 IDIs.
I'm not really going to argue with you there, except that I do think they are quite efficient matched to a 1.6lTD, but only at high engine RPMs. And I'm sure with modern ball-bearing and/or variable vane technology, one could come up with one that's even more efficient. I just can't on my car, because there's no way that would survive a protest at nationals. And I would likely be protested for such a modification, were I to win at nationals in my diesel. I'm the only one who's raced a diesel at all at SCCA nationals! There are over 1000 racers competing in nationals each year. If I were to win my class in a diesel, you better believe I'd have people crawling all over it looking for protest-fodder. It's also going to make some major waves in the racing community, which I would love to see happen. :o Just to get back at everyone who told me that it was impossible for a diesel to be nationally competitive. ;)
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do you think if that intake could resist at high pressure? 1.5 bar or 2 bar?
what's about the 2l cross flow intake? we don't have it in france....
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do you think if that intake could resist at high pressure? 1.5 bar or 2 bar?
what's about the 2l cross flow intake? we don't have it in france....
The 2l cross-flow intake has actually quite short runners if you actually look inside and measure them, they might not even be 6" from plenum to the surface where upper and lower manifolds both together... also it would be much more difficult to adapt the upper part to a 1.6lTD than an SDI manifold would be. I'd sooner go to a 100% custom-fab mandrel-bent tubular manifold than a 2l crossflow manifold for my project...
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Regarding your stock exhaust manifold, have you considered extrude honing? I don't know how much it would be, but at least you don't have to change the location of the turbo.
Peter
I doubt there would be any gains, to be honest. I have already port-matched the exhaust manifold to the head, and stock it seems also very close to ideally matched already to the turbine inlet. The inside walls are very smooth (yeah I did clean that up a touch, but was very nice smooth casting actually bone-stock as I recall, and also the ceramic coating probably added some additional smoothness). The inside walls also do not narrow down at any point, so I don't see the airflow coming out of the head into the exhaust manifold seeing much of a restriction. Enlarging the tracts inside the exhaust manifold further could actually be worse than stock, because it would mean the gasses have to narrow down more also before they can pass through the narrow slot before they hit the turbine wheel.
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PROBLEM FIXED!!!!!!!!!
Details here (http://forums.tdiclub.com/showthreaded.php?Cat=&Number=797902&page=0&view=collapsed&sb=5&o=31&vc=1).
Sorry, I'd retype it, but it's almost 12:30 a.m. local time, and I've just worked on the car for 13 hours.
Take care :)
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i have an intake manifold from an eurovan 2.4d 5 cylinders.
for a tdi it would work great! just need to cut one tube.
if i found some picture i will post them.
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I found a study of varying intake runner lengths on a Jaguar racing 4-cylinder engine with fuel injection and non-carburated (individual throttle bodies) Interestingly, it is also remarkably old study that it comes from a book "Scientific Design of Intake and Exhaust Systems", published by good ol' Robert Bentley in 1972.
The study shows volumetric efficiency vs rpm (equivalent to hp or torque vs rpm) curves plotted for various lengths of intake ports that were all the same (about 2") diameter. There was no mention of cam specs on said engine, or displacement. The lengths of the "air horns" fixed to the end of the intake manifolds were given (tested at 0", 8", 15", 21.5", and 32.5"), but the overall lengh of the induction tract between intake valve and end of intake manifold was not given. However, using the organ pipe tuning equation and looking at the localized peaks for the various lengths, I was able to solve for the overall length of the intake tract, and I found it to vary from 4.6" to 37.1". I also determined the reflective values observed in the plots for each resonance peak. The lowest reflective value observed at the highest RPM for the longest induction tract length was only the 3rd RV. 4th RV was then the lowest RV for the 21.5" air horns, and 5th RV was the lowest RV for the 15" air horns.
What I was surprised to find was that even though no lower than the 3rd reflective value was used on the longest intake runners tested, the effects of the stronger reflective values was still dwarfed by a gradual, overall loss in high-rpm volumetric efficiency for the longer intake tracts (perhaps this was because the 2" intake diameter was sized too small for the engine, although that is speculation.) This makes me think before deciding on 24" runner lengths, only looking at the organ pipe equations. I better do some testing on my 1.6.TD before settling on a particular runner length. I better get proficient at fabricating test intake manifolds and buy some extra material so I can make some varied designs. Picking too long a runner length could sap high-RPM power too much, and the organ-pipe tuning equation doesn't seem to predict this important effect at all.
But there was also something positive looking at the study that is clear, that some of the very short runners were down in power across the entire RPM range. IE: adding a little bit of length to the runners was good for quite generous (IE: up to 15% increase) in volumetric efficiency. That kind of a gain from a custom intake manifold on my 1.6lTD, for improving my racing setup would be HUGE!
Once a runner that is ballpark-length close to ideal is found, the pipe-organ tuning equation could be useful however to predict how the local RV peaks will shift around.
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Hmm, I think I have a copy of that book. I'll have to check tonight! :D
In the meantime, Jake, I think that the benefits of very long intake runners to a boosted engine are probably minimal. I am going to try this GTI intake on mine.
(http://home.earthlink.net/~rps1976/Images/Diesel/IntakeEndView.jpg)
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I am definitely looking forward to hearing how that works!
Edit: hey, that might even fit on your quantum fairly easily too, right? There is adequate clearance in the area, maybe, to just bolt it on in place of the current 1.6lTD manifold? Maybe all you'd have to do is fab some boost tubing and you'd be in business!
You might have to borrow my G-tech pro competition accelerometer before you do this, because I want you to take baseline power curve measurement and also one to compare after the manifold swap. IMO, seeing the power vs rpm curves really helps us understand what's being effected by such a change as intake manifold swap! IE: I'd like to see at what RPM and relative magnitude the peaks and valleys are on the power curve before vs after. Let me know if you are interested; I could mail it to you! I don't have any use for it at least until my Rabbit's engine is back up and running (which could be a while... potential full-motor rebuild time.)
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Jake, the reduction in VE due to extremely long runner intakes is due to the boundary layer flow loses due to the surface roughness. That's why, as you noted, much more has to be considered when tuning than just one parameter, such as resonant frequencies.
It should be noted that the plastic upper intake manifold has a smoother surface finish than any aluminum casting.
Here are some comments in a post related to the subject:
Unfortunately for finding a definitive, quantitave answer to whether the manifold contributes to better performance; within the last two weeks I have been using yet another chip program from what I had been using before (Ups --> ST USA). It's quite aggressive on fuelling (it was smoking like a tire-fire before last weekend's fix, but it has cleared up beautifully now, so that speaks a lot IMHO).
So, although I can't give you a quantitative number, the benchmark for comparison now would be to beat my best 1/4-mile time of 17.079 or 1/8-mile time of 10.787, both of which were achieved a week apart in late August, 2002 (my best 2003 1/8-mile time was worse at 10.87, despite .2 - .3 second better 60-ft times, reflecting a detuned chip I was running between July 2002 - July 2003 to control smoke). Hopefully I'll be able to go out and post timeslips soon...
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Ahh, the boundary layer explanation ("air friction") makes sense - however, there is a picture of the Jaguar race engine with these "air trumpets" installed, and they appear to be smooth-wall metal tubing, not rough aluminum castings... I would expect they would be pretty close in surface smoothness to your plastic SDI runners... but, we are missing a lot of other factors in this case like engine displacement and cam timing, and how the diameter of the intake runners compares to the rate of air that is flowing through them. IE: perhaps even at nearly 2"ID, the jaguar engine's runners are still undersized.
Anyway, I think you are definitely right that you need to consider other factors than the pipe-organ resonance equations. It was interesting how using the equations, I was able to accurately describe the locations of each of the 3 lowest reflective value resonances in the 3 longest air horns being tested. The observed locations of the resonances matched quite closely the calculated locations. That tells me the equations are accurate at least for when the runners are fairly long (IE: long enough to make use of the 6th RV or lower) for comparing relatively how the resonances move by making fine-tuning changes to the lengths of the manifold runners. Pretty cool!
The problem with measuring a modification like the SDI manifold only via 1/4 mile ET and trap speed results comparisons, is that if the manifold beefed up low-end torque but caused a loss in top-end horsepower let's say, (which I think is quite a plausible scenario I'd like to know if it's the case) the 1/4 mile ETs might show no change or a little benefit, but yet I'd like to know if the change in manifold caused this sort of change to your torque & hp vs RPM curves. Also, since your TDI has a much lower redline I'd guessing than my IDI does, if there is a trend resulting from the the SDI manifold of hp dropping off near you motor's redline, it sure would be nice for me to be able to know that as it would probably be more acute on an IDI motor revving toward or beyond 6000rpm.
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As you noted before, anything compared to the sorry-excuse-for-an-intake-manifold-design as the stock TDI one is, would be an improvement. The stock manifold has absolutely NO runner length whatsoever and a plenum (if you want to call it that) volume that's barely half of the engine's swept displacement.
VW apparently gave zero regard to tuning (which is reasonable for a forced induction diesel motor), but instead arrived at a design that would package well and be the cheapest to manufacture and use the absolute least amount of aluminum that would resemble an intake manifold :D
I would be interested in learning more about the calculations you did, Jake. I am quite familiar with the Helmholz method to determine resonant frequencies, but I've never done a hand calculation before. I have created a bunch of engine analysis and calculation spreadsheets over the years; I'd be willing to share them and I'd also like to develop one for the manifold design as well if it hasn't already been done.
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I have developed a couple excel spreadsheets... one for testing the real-world validity of the organ-pipe tuning formulas using the racing jaguar intake manifold study data I found in a book as the test (you can see the results for yourself), and another that does the organ pipe tuning equations to calculate tuned frequencies of the various reflective values for a given motor for various intake runner lengths. They are both sort of quick and dirty but you will probably be able to figure them out. ;) The main piece of data you need to know for a motor to make use of the organ-pipe tuning equations is the intake camshaft duration. I have that info for the 1.6lD/TD motor, I'd bet it is similar for a TDI, but if you know it that's even better.
I will see how I can get these spreadsheets to you... E-mail would be easiest, but maybe there's a way I can get them up on the net (too bad I am out of server space...), let me think about that. Also to accompany the jag tuned freuqency spreadsheet, I will try and scan in the VE vs RPM plots of the racing jag motor from the book.
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Jake, you've got mail.
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Jake, the reduction in VE due to extremely long runner intakes is due to the boundary layer flow loses due to the surface roughness. That's why, as you noted, much more has to be considered when tuning than just one parameter, such as resonant frequencies.
It should be noted that the plastic upper intake manifold has a smoother surface finish than any aluminum casting.
I just got done reading my new book, "Scientific Design of Intake and Exhaust systems" (1972, but amazingly the points it makes explain a great bit of modern engine design!) Quite the in-depth read. ;) The author rigged up cool apparatus that was capable of reading pressures inside cylinders, exhaust manifolds, and intake manifolds as it changed over fractional rotations of the crankshaft movement during engine running. It explains a lot of very interesting things.
Anyway, I now have a definitive answer as to why too long of an intake runner saps high speed power. What happens with a long intake runner is, early in the intake stroke, as the piston moves down, airflow is lazy with the long runner, due to it's long length and high mass of air, it resists movement initially, and there is a build-up of vacuum inside the cylinder. This build up of vacuum causes the rate of airflow through the intake runner to increase to very rapid rates, and that airflow given enough time (low enough engine RPM) overtakes the expansion of the chamber related from the speed of the piston, and if it has enough time before intake valve closes, can even "supercharge" the cylinder. At high rpms however with too long and narrower runners, the delayed filling of the cylinder during the intake stroke doesn't have enough time to "catch up" with the vacuum generated inside the cylinder at the early part of the stroke.
There was mention that this effect could be reduced by porting: enlarging the diameter of the hole behind the intake valve and the rest of the length of the runner behind.
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Makes perfect sense to me :D
[Furiously taking notes for book title]
Also a great (but not light) read is Turbocharging the Internal Combustion Engine by Watson & Janota.
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hey ! i think there is a good book in english! do you know where i can buy this book?
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yep! i go to amazon then i will receve : Scientific Design of Intake and Exhaust systems,
but the other is not dispo :(