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Engine Specific Info and Questions => TDI Engine -General Info => Topic started by: Helliouse on April 21, 2008, 01:55:23 pm
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Are they interchangable?
Has any one looked at or tried to find out the seat pressure of a TDI valve spring compared to a 16/8/VR6 valve spring?
Just found a place that is selling heavy duty (looks like) dual spring valve springs, and want to see if there are an option.
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you mean to tell me no one has the OD or ID for a VW gassers valve springs?
ALH
ID - 23mm
OD - 30mm
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i would imagine diesel valve springs to have more tension... and be able to take more of a beating.
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I'm not sure why many people would be wanted to pay the dough for "better valve springs" especially considering what the benefits of better valve springs are...
The benefits?
They are more served in higher RPM applications in a gasser where you may have extended the RPM range of the motor via various building characteristics, bigger cam, etc. that would extend than range. Reduce valve float, potential of the springs breaking...the seats, etc.
In a diesel...umm...ok, i guess if you want to spend the dough there :) go ahead. It won't give any benefits beyond knowing that you have "titanium valve springs" in there instead of the stockers. If our engines saw 6.5k plus....maybe, but the stockers are more than adequate for the motors revving needs.
Most diesel applications also..run dual springs. A cheap mod for 8v motors used to be running double diesel springs because they are "firmer" without spending the dough for "hi performance" valve springs.
My .02
Joe
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Joe has it right, but Helliouse IS wanting to go with big(ger) revs.
Contrary to what jtanguay was thinking, diesel valve springs are considerably LIGHTER than gassers. This is due to a lot more conservative cam timing (rates of acceleration of the valve when opening) and much lower RPM range.
If you diddle with gassers, you would also have noticed that for Canucks at least, the 1.8 ACC engines also use 7 mm valve stems and single, diesel-like springs - even with fairly large valve heads (which are also somwhat tuliped). The reasons for lighter springs wherever possible is efficiency (it takes a LOT of energy to compress these things thousands of times a minute), longevity (more valve spring pressure = more cam & lifter wear) and heat load (see efficiency - where do you think the energy from all of that extra power for stiff springs goes??).
IF Helliouse wants to go big, I suggest he contact PP for a cam and get his spring recommendations.
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What about usable powerband? Cost vs. benefit of being able to expand the RPM range....to say 6k on a TDI?
Yes, diesel valve springs are considerably lighter, but the upgrade in valve springs is more in structure and strength (I think is what you are saying in part) (your paying for this in the upgrade when you buy upgraded valve springs for gassers) not nessarily "tension". There is a considerable degree of valve float I think in using stock gasser springs on a crazy gasser motor...and the upgrade in valve springs helps this factor slightly but moreso, increases the amount of abuse that the springs themselves can take without fatiguing. Hence titanium springs, retainers and the lot.
I can see the reasoning in getting them there...for that reason...but can't see the cost vs. benefit of upgrading in buying them...
Springs alone....eh... springs and cam....as your suggesting...maybe. However, would the diesel springs be ok? I think so...
The cam won't expand the 1.9 that far (even though a few benefits have been shown).
NOW....on a 1.5 or a 1.6 IDI diesel...hmm....
Still...have to look at the meat of the powerband and where the power is really used. Just don't think your going to see the benefit you'd want to see in trying to expand the RPM range of the motor in question. Though...are you going for even further mods with the motor...possibly in the area of stroke, etc. with this motor? That could bring things into a different light...
Joe
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You guys also have to remember that running higher amounts of boost will test the valve springs as well and cause them to float more easily. If he's going for higher RPM's and significantly more boost then I think wanting stiffer valve springs is justified. You really DO NOT want valves floating in a Diesel engine at high RPM's.
And, it does in fact take more energy to compress stiffer springs with the cam lobe, but you also have to remember that the stiffer springs also push up the backside of the cam lobe, i.e. after the "peak" as well so a bit of that energy is re-claimed as efficiency. As with everything, I'm sure there is a point in stiffness where returns are diminished, but every little bit helps.
Brendan
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We should try and figure the limits of the stocker springs I think...before looking at that end of things. I'm just thinking about cost vs. benefit at the moment.
I've had no problems with my setup (still stock cam...want to get ahold of an AAZ unit) in the mk1 and I push 30-35psi.
Hmm...looks like some testing is in order..
Joe
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there was a good dicussion on this in the TDIclub pages somewhere. IIRC, the double spring upgrade offered for the TDI is actually a stock double spring from a VW gas engine..can't remeber which one. If you do a search on there you should find it. I think there was a discusion on "Shortysclimbin" engine build as well.
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I thought all they did over there was talk about colored lug studs and wheels,, :lol:
Maybe the occasional "what stereo should I get?"
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Wow, nice discussion guys. Thank you.
So, I guess I should post a little more on what I am doing.
Looking at over 30+psi, bigger cam, and valves, with P&P; the only way we can build power over 5500 rpm is getting a higher VE in the upper rpm, and then force feeding the air to it.
My concern with stock springs is 25+psi and 5500 rpm, let alone anything higher; as I have heard/read posted that the chances of valve float increase with pressure behind the valves. Also read that the diesel springs are quite a bit lighter, I haven’t looked to much more in to it as of yet though. I will be looking for shortysclimbin’s build.
I am going to see if I can find someone local to test my springs, and see what the seat pressure is as well. If any one has a set of gasser springs could they test them? I know a big VW gasser fan here, and will see what he knows about the springs.
I have found a place that sell the 8v dual springs for up to 7k rpm, for a real good price, so that is the reason for the questions.
In the mean time keep up the talk, it’s great!
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:wink: quality convo is always good stuff. Nice to see more info on the build as it makes more sense now :)
Joe
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guys,
Glad to see your taking info on my build up but please dont think I have it all figured out ;)! I will test the valve springs and let you know how they work out. I was experiancing floating effects at around 4k on the local dyno here when I was pushing 26psi on my last motor I did up. From what others claim this should help things drastically. The seat pressures are key though!
Helliouse, I hope you understand where I am coming from and saying its untested yet. If you would like to talk theory and really dig into things let me know. I just dont like handing out info to people who take it as fact when I truely dont know if it will work or not until I have tried it.
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I'm using Crane Cams dual springs on my 8mm (valve stem) AAZ head.
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How many miles were on the old springs? That should be something to take into consideraton and makes me wonder on the next mTDI I'm building right now (that was worn enough to need the first OS). However, I experience no such problems on the mk1's mTDI (which was fairly low miles before I got it/rebuilt it....at 126k).
They would faitgue over time.
Probably at sustained higher RPM's etc
Joe
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FYI, in my short time working for VW, the ONLY major mechanical issues I ever saw with TDI's was valve springs failing- spring would crack and collapse, valve would drop, piston hit valve, then valve would drive a hole through the lifter, then shear the cam. Not pretty. Saw two of these instances in a year of working at the dealership. These were both bone stock cars with a moderate amount of mileage.
Edit: I'll add that I never saw this with any 2.0 gassers so it would be safe to assume that the TDI springs are lighter-duty, as there is no other logical reason why they would fail in a TDI if the camshaft profile is more mild and it sees less RPM's. A quick ETKA check shows different springs for the 2.0 and the ALH. I always thought they were the same.
Brendan
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Hmm...I am wondering if the "HD 8v Valve springs" that Autotech sells are an upgrade from some OEM spec motor. I found a new set of them locally for 65.00. Might be worth my interest...
Joe
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Here is some information I have found.
Installed height
30.6mm / 30.5-31mm - 1.2007874"
ID - 23mm - 0.905511811"
OD - 30mm - 1.18110236"
Seat pressure that I have read tossed around for seat pressure, between 90 and 100lb.
The only stumbling block right now is spring rate, what rate do we need.
I have found some bee hives that will work but it will require some removal of material...about .2"(7mm) from the spring seat, not including a washer to prevent the spring machining into the head.
My only concern is they had a video of these springs in action, and they where bouncing at 6500rpm, cam profile plays a big part in this; with ours being so very mild... :?:
:!: Note: I am just researching, if you choose to buy these and use them…that’s your choice. I am, in no way, recommending them, or saying they will work.
http://www.pacracing.com/Beehive_Springs-PAC_1223_Set_of_16.html
OD: 1.105" - 28.067mm (Big End)
ID: 0.742" - 18.84mm (Big End)
90 lbs @ 1.470" (Recommended install height) 37.338mm
252 lbs @ 0.970" 24.638mm
Lift: 0.500" 12.7mm
Max Coil Bind .900" 22.86mm
Spring Rate 324.0Lbs/in
Spring Weight 37.6grams
If I find anything else I will post.
If any one knows how much we can take out...
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Hello,
Can any one confirm these numbers?
Valves dimensions
7mm stem dia.
0.275590551" Dia.
96.9mm total length
3.81496063"long
3x 1mm Valve Keeper Groves Rounded
10mm Bottom of low grove to top
1mm back cut angle width
Intake Valves
36mm dia. valve
1mm margin .5mm bevel
2.5mm Seat
Exhaust Valve
31mm dia. Valve
2mm margin
2.5mm seat