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Engine Specific Info and Questions => IDI Engine => Topic started by: rabbitman on December 15, 2009, 12:46:39 pm
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I got so tired of it not working right that I yanked it last light.
I had a 2.5" pipe bent up for the DP then cut the toilet bowl off the stock DP and welded it to the 2.5" pipe , so now it's 2.5" all the way back!!! ;D I left the gasser intake installed.
It's rather loud, when I floor it it's pretty loud then at 3000rpm some kind of resonance starts and it get's WAAAY louder, sadly it's sounds quite like a ricer at that point :-[.
My thermocouple can no longer read all four cylinders so I put it where the number 2 and 3 exhaust runners meet. I didn't touch the fuel settings in taking the turbo off.
With turbo the egt's would soar above 1300F and then I would let off, now without the turbo the egt's get somewhere around 1150F max all the while belching that wonderful black stuff out the tailpipe :D.
It's a real slug too, possibly due to an intake restiction since the inlet into the manifold is only 1.5".
I wish I could have the turbo tested to see if it really was the problem or if it's some other part of my setup, but alas, I don't feel like parting with the dough it this time :(, especially since the wheels look perfect and the bearing's are good.
I read about other people's vnt's making tons of boost while mine even with the vanes closed never even pegged the 15psi gauge........
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Yeah I'm sure my intake is restricted, it is soooo gutless compared to before I ever turboed it.
Seems like it's got no power band, like if I mash the go pedal in second @ 1000rpm it'll pull out and speed up real even.
The other weird thing is at WOT it smokes black yet the egt's isn't as high as before turbo, my theory is that it's starving for air and thus can't burn hot enough to make excessive heat. ???
I'll mod the intake and see if it helps.
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1.5" inlet is awfully small compared to say a stock N/A intake.. I'm not overly turbo savy, but could the small intake be causing your boost issues???
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1.5" inlet is awfully small compared to say a stock N/A intake.. I'm not overly turbo savy, but could the small intake be causing your boost issues???
I've wondered if it could be the cause, in my build thread I had pics and asked about it and nobody seemed to think it was a problem. :-[
I know to have boost pressure you gotta have flow and if it wasn't flowing good enough thennnnn......I don't know. :-\ Maybe it would surge but it never did, I should've tried to put a boost guage right at the compressor outlet and see what it read.
I've never delt with turbos at all until this so it has been quite a learn. Maybe I'll fix up the intake inlet better and try the turbo again, it's pretty easy to put it back in just takes time is all. 8)
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i think the stock TD manifold is grossly restrictive. is that the one you have on there? anything is better than a stock TD manifold if you dont have boost going through it.
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i think the stock TD manifold is grossly restrictive. is that the one you have on there? anything is better than a stock TD manifold if you dont have boost going through it.
I'm using this gasser mani off a '80 1.6L bunny.
(http://i249.photobucket.com/albums/gg218/rabbitdude82/Rabbit067.jpg)
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I'll guesstimate that the exhaust gasses are less dense and therefore are not heating up the EGT probe as much/quickly as when you had the restrictive turbo on there.
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i think the stock TD manifold is grossly restrictive. is that the one you have on there? anything is better than a stock TD manifold if you dont have boost going through it.
I'm using this gasser mani off a '80 1.6L bunny.
(http://i249.photobucket.com/albums/gg218/rabbitdude82/Rabbit067.jpg)
yea, with a turbo hooked to that it would be fine. but with no turbo it would probably be a wee bit restrictive.
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When you had your manifold off, did you plug the ports to keep crud out and forget to remove whatever you used as plugs?
Nope no plugs, I just don't drop things were they shouldn't go ;D
Yeah this is weird, my top speed is around 70mph and it's smoking black the whole time. Before turbo I could go 80-85......kinda. Bottom end power isn't too bad though.
I thought the fat exhaust would help a lot but it just makes it really loud.
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Perhaps your exhaust is too big. I noticed a drop in power when my muffler fell off. At least I think I did. The butt dyno lies...
What air filter are you using?
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Perhaps your exhaust is too big. I noticed a drop in power when my muffler fell off. At least I think I did. The butt dyno lies...
What air filter are you using?
The air filter setup is the stock NA plastic part (minus the "snorkel" piece) sitting where the stock td airbox would sit with the top part off the 1.7 carbed gasser. That has a 2 inch aeroduct connecting to the 1.5 inch hose that goes into the gasser intake. Confused? ;D This useless 'puter won't connect to the camera or I'd just post a picture of it.
Overall the only part smaller than stock is the 1.5 inch hose/intake inlet.
I think part of why it feels gutless is 'cause it SOUNDS like it should have lots of power, however a top speed of 70ish is rather lame.
Yes it could be that the exhaust is too big, contrary to what most think, these do actually have slight valve overlap.
If I'm correct in thinking that the velocity of the escaping gasses is supposed to help draw fresh air in then I've messed that up with the fat exhaust so that affect is gone.
The valve overlap (probably) wouldn't affect a TD since the turbo doesn't allow it to free flow anyway.
I almost went with a 2" or 2.25" dp rather than 2.5" but it's a little late now.
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That overlap is why my head builder said you will get gains over 20 psi on the TD engines, but it is diminising returns. He said I will blow it past the valves a little.
Maybe you could route it a little differently for a ram air setup and you should be happy with it.
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Do you have a VAC gauge? If so, plumb it to the intake manifold where you were reading boost and see if you are registering vacuum. If you are, then your intake is too restrictive. The 2" aeroduct might be the issue.
Why do you think the aeroduct would be the problem when I have some 1.5" in the line?
Good idea on the VAC gauge. :D
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I'm sure you know this but you would be best to preform the vac test at 70mph, or redline in whatever gear of your choice.
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I hooked up a manifold pressure gauge yesterday and at 4700rpm (about the highest I ever go) the pressure went from 28.75inhg down to about 26.5inhg.
I know it's best to not have any drop but I don't what's acceptable.
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That's a huge vacuum,.. about what the brake booster pulls.
Hard to believe it pulls that hard trying to get air,..
but i've never measured mine.
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That's a huge vacuum,.. about what the brake booster pulls.
Hard to believe it pulls that hard trying to get air,..
but i've never measured mine.
Yeah, I'm perplexed by those numbers. 0 inHg is atmospheric pressure. 29 inHg is HUGE vacuum.
I'm not an expert on this stuff in the slightest but 0 inhg is a complete vacuum and 29 inhg (rounded off) is atmospheric pressure at sea level, it changes slightly with the weather. I'm at 1100ishft so it's a little less.
The manifold pressure gauge says 28.5ish inhg when the engine isn't running.
This has a good picture at the bottom showing how inhg works: http://hyperphysics.phy-astr.gsu.edu/Hbase/pman.html (http://hyperphysics.phy-astr.gsu.edu/Hbase/pman.html)
Us diesel guys don't know much about inhg because of the lack of a throttle plate, I'm only starting to understand it from talking to Dad (he's sometimes a small aircraft pilot) about it. He doesn't understand what a boost gauge is, we see 0psi as being no boost but really it's atmospheric pressure pushing the air into the engine at 14.7psi.
The piston isn't sucking the air in, the atmosphere is pushing air in to fill the void created by the piston going down ;D.
A boosted aircraft (just because they have a intake mani pressure gauge) would read something higher than 29inhg, like 40 or 50inhg......wierd stuff.
Soooo, back to school everyone :D
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Random. That's the exact gauge I'm using in my golf right now.
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most automotive gauges show boost and vacuum as the difference between the pressure in your manifold and the true atmospheric pressure.
our boost gauges show 0 as no boost even though true atmospheric pressure is 14-ish.
we all just assumed you were using a more standard automotive gauge thats all.
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it takes no vacuum to pull no mercury (inches of HG) ie, lower number.
if you have a large vacuum, then it pulls lots of mercury, indicating a large vacuum.
so, yea, andrews correct on this. you should have like NO VACUUM in your intake system. the closest you can get to zero vacuum, the better your crap is gonna flow.
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yea, if we were talking about vacuum in general, rabbitman would be right. but we are talking about a specific kind of vacuum..
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yea, if we were talking about vacuum in general, rabbitman would be right. but we are talking about a specific kind of vacuum..
Yeah but with the gauge I'm using I don't really have a choice of which kind of vacuum. ;D
Here's a close pic of my gauge, it's the one on the top and the difference is mine goes to 75inhg rather than 50inhg: http://www.aircraftspruce.com/menus/in/manifoldpressuregauges_uma.html (http://www.aircraftspruce.com/menus/in/manifoldpressuregauges_uma.html)
It's sitting at 29.5inhg because it's almost down at sea level.
So I lost about 2 inhg at 4700rpm and I don't know if that's enough to cause a noticeable power drop.
Andrew, I've seen those gauges like in your picture and they don't make any sense to me ::), I'll have to show Dad and see what he thinks.
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i think the stock TD manifold is grossly restrictive. is that the one you have on there? anything is better than a stock TD manifold if you dont have boost going through it.
I'm using this gasser mani off a '80 1.6L bunny.
(http://i249.photobucket.com/albums/gg218/rabbitdude82/Rabbit067.jpg)
Dude, you need a bigger inlet on that thing! put a pipe on a couple of inches in diameter bigger, should see a lot less vacuum. BTW, what are you using to pipe the air to it? is it collapsing when under load??
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Patrick, from the airbox I have a 2" aeroduct that goes into a 1.5" rubber hose. It's rather lame I know but I'm sure it's not collapsing.
The difference is that your gauge is an aircraft gauge which measures "absolute" pressure rather than measuring manifold vacuum.
I wish I understood all this better, so it all depends on what ya call 0psi or 0inhg then.
So...........arrrg I just lost my thought.
Andrew on that gauge picture you posted what would it show if it was on a NA gasser that was idling? What about full throttle?
'cause on the aircraft gauge idle would be about 10-12inhg and full throttle would be 28-29ish depending on altitude. Thanks for all yer guyses input ;D
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it shows high vacuum at idle, and you want as close to 0 vacuum as possible at full throttle. or boost if you are in a compressed application.
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Just talked to Dad about it, showed him the pic of the boost/vacuum gauge.
We figured out the numbers labeled inhg are not correct, like when it says 10inhg it's really negative 10psi, and scientifically it would be called 19inhg ;D
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So If I have this right, you are pulling a 2.25 PSI vac across your intake duct?
If so, I'd class that as 'strangled'
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Yeah I think I see what you're saying, it not all clear in my mind yet though ;D
That bit about vacuum being compared to a higher pressure is what threw me off with the aircraft gauge then along comes the auto vac gauge and really screwed me up. But I think I kinda got it though.
If I could find a 2 1/16" manifold pressure gauge I'd probably want it, I've not found any and I bet it wouldn't be cheap if it was gettable.
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manifold pressure gauge? never heard of one. what do they read? psi like a boost gauge? or what?
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They read pressure in "inches of mercury" and the zero of the scale starts at zero pressure (or total vacuum). Because of that, 29.92 inches of mercury of pressure is equal to 1 bar or 14.7 psi or atmospheric pressure at sea level. A vacuum gauge that has 0 set as atmospheric pressure will read 29.92 inches of mercury at total vacuum and be an inverse of the manifold pressure gauge.
HAH....THE LIGHT TURNED ON. Yup that makes sense, I was having trouble wrapping my little brain around it. :D
So If I have this right, you are pulling a 2.25 PSI vac across your intake duct?
If so, I'd class that as 'strangled'
Is that the case? A 2.25 psi vacuum? huh, my brain isn't totally wrapped around this yet I guess ::) Maybe I'll get workin' on a better intake system.
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Bad language form on my part.
Just for exercise, I'd unbolt the plate from your intake, tape a filter on there(or to the gasser throttle body if you have it), and make a pass to see if smoke is gone.
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2.25 in.Hg isn't equal to 2.25 psi. It is about 1/2 that. 29.92 in.Hg equals 14.7 psi.
Oh yeah ::)........so I suppose a better intake would hardly even be noticeable, but of course I'd rather not have any restriction at all.
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Yeah this is weird, my top speed is around 70mph and it's smoking black the whole time. Before turbo I could go 80-85......kinda. Bottom end power isn't too bad though.
I thought the fat exhaust would help a lot but it just makes it really loud.
I have 2.5 from the turbo back, then splits to dual 2.5 under the back seats and it's not that loud at all with the turbo.
My build is nothing like yours but for some perspective... if i keep the boost around 15 psi my build will make my 4-door jetta get up to 93mph quick and climb to 115mph quite slowly after that at wot (20 psi) but it will get there. I've always ran out of road, i don't know where the limit is.
synopsis of my mods are:
aaz head
1.6 bottom end
limitless boost on a T3
Gov mod (disabled)
fuel screw turned in as far as it will go
stock nozzles
timed to who knows what, really advanced - i know that much.
2.5 inch exhaust as i mentioned
an intercooler (8tallx3deepx27long)
tdi alh intake (which i think is restrictive but maybe not (i cut it at the elbow)
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my rabbit would go like 75 top speed when it was a n/a 1.5, now it goes almost 140 mph @ 25 psi (ran out of road like ed) before it hits the governor. except, unlike ed, my car is slower to 80 then it is to 100, once i grab fifth gear, it just starts pullin like a mother. i really dont even know where the top ceiling of my governor is, really high, i know that. my GTI will pull till like 6000 rpms on the tach, my diesel pulls till who knows when, and you can get more mph out of every gear between shifts with almost identical transmissions (9A in the GTI, AUG in the diesel.)