Decreasing Turbo Lag [Archive] - DSM Forums: Mitsubishi Eclipse, Plymouth Laser, and Eagle Talon Forum:

: Decreasing Turbo Lag

11-07-2005, 08:24 PM
Ok all us dsmers know when its time to upgrade(every day it seems for me) but i am at the point to where the mods i have don't satisfy me anymore. No i know i have alot more to do but as of now i have: FMIC w/ custom 2.5in Piping, Buschur racing T-28 turbo, complete 6bolt motor swap into my 95 tsi, turbo xs rfl blow off valve, turbo xs manual boost control, ACT 2600 clutch, and K&n filter. Now my boost only hits 14lbs in a second gear pull. However i have a tremendous amount of turbo lag... now i know that a big part of this is my stock exhaust but if i upgrade to like a N-1 cat back from apexi how much will this be decreased. I don't get full boost untill 4800 rpm and it sux cuz during shifts i loose lots of speed cuz my turbo won't spool...the reason i got the t-28 over a 16g or a 18g is because i thought that using a bored out t-25 would maintain that low inirtia and would spool alot faster than a 16g but its not the case with me. I am about 95 percent sure that its not a leak cuz i've had all my coulpers press check and the bov( i know many say the rfl leaks) it doesn't. Where do i go from hear... Exhaust... how much lag do i loose with exhaust?

11-07-2005, 08:29 PM
Dude you should be spooling well before 4000 rpms My 20g gets 21 psi by 3900! Are you using a maft? as I remember the rfl vents to atmophere? Your mbc on right?

11-07-2005, 10:44 PM
I believe you should be checking for leaks on the exhaust side, such as the exhaust manifold, downpipe, and O2 housing.

It's good that you checked the other couplers and stuff, but that would be a boost leak, and not an exhaust leak. The exhaust is what spools the turbo, so a leak there can cause a turbo to lag more than usual.

11-07-2005, 10:47 PM
i dont hit full boost, 20psi, until 5,200 rpm with my gt3040

11-08-2005, 12:11 PM
Hey guys i just found out that i have a hairline exhaust leak right on the left corner of the manifold where it hits the gasket it is small and just bubbles the air out but still its a leak would this create that kind of lag??? thanks

11-08-2005, 12:34 PM
i would not think that a small leak like that would cause lag like you have, a 3" dp and exhaust should help you out alot.

11-08-2005, 02:05 PM
if the hairline crack went all the way through than it woudl def be your prob. also when you change your exhuast manifold i would check the exhuast housing of the turbo and look for cracks....

11-08-2005, 02:14 PM
I've got a broken headerstud in the head, with a major leak at that point, and my turbo still spools at 2800rpm, same as it did before the leak. I would pressurize your intake system, see if you have any leaks in your intercooler, or intercooler piping, or intake. Leaks there will show, because the turbo is working harder to pressurize everything. A T28 should spool up as fast as a T25 did.


11-08-2005, 02:38 PM
a hairline leak should NOT effect spooling time .... the leak must be big enough to effect the pressure difference between the manifold and the 02 housing for there to be an effect

a turbo spools because the pressure in the manifold is HIGHER then the pressure in the exhaust, therfore a leak in the exhaust system will cut spool time down, just like a larger exhaust would

or maybe im just imagining that my budies car was spooling damn nice with no turbo/manifold gasket and no exhaust ....

11-08-2005, 04:13 PM
Well when i rev the car at idle from the tb i can see white smoke spitting out of a spot in between the gasket and the manifold at the top left corner... now i have heard of this stuff called hondabond i think that should seal high temp connections has anyone had any luck with this stuff???

11-09-2005, 01:47 AM
Well when i rev the car at idle from the tb i can see white smoke spitting out of a spot in between the gasket and the manifold at the top left corner... now i have heard of this stuff called hondabond i think that should seal high temp connections has anyone had any luck with this stuff???

First off, the throttle body does not get that hot. Secondly, the there should be no smoke coming out of your throttle body. The throttle body is connected to your intake manifold, and the turbocharger is connected to the exhaust manifold. Perhaps you are talking about the exhaust manifold?

Either way, why not just replace the gasket. If it is a gasket on the throttle body, its pretty simple to replace and should take well under an hour. If its a exhaust manifold gasket, that may take a bit longer, depending on the condition of the exhaust studs. Check to see if any nuts are loose as well, and tighten as necessary.

11-09-2005, 04:22 AM
Perhaps you are talking about the exhaust manifold?

The majority of this thread has been about the hairline crack he has in his exhaust manifold, so I would ASSume thats what he's talking about. ;)

11-09-2005, 11:37 AM
No... the smoke comes out in between the exhaust manifold and gasket not the tb... I said that to indicate the fact that when the hood is popped and i rev the car from the tb to look at the manifold i can see the leak in the manifold...thanks outofideas

11-09-2005, 11:38 AM
none of the studs or nuts are loose that was the first thing i checked they are all as tight as they can be...

11-09-2005, 12:42 PM
Exhaust leaks pre turbo and boost leaks will effect spool time. To make a small turbo like the spool that late it would be a pretty big leak. You don't hear any of the typically pffft...pffft....pffft of an exhaust leak anywhere? Mani is sealing tight ot the head? Wg is closing completely and sealing solid?

11-09-2005, 02:20 PM
Wg is fine and the gasket seals to the block but to the manifold it just leaks a little on the top left corner.. could it be because i am using my 2g manifold instead of the 1g? nope there is no typical sound that you commonly hear from an exhaust leak. its weird because it feels like i am spooling a something alot bigger than my t-28

11-09-2005, 05:27 PM
1G to 2G differences wouldn't account for this. Has the car been like this since you installed the turbo?

11-10-2005, 05:25 PM
No when i first installed the turbo i noticed a little later spool than the t-25 but recently i have noticed the extremely late spool.

Orange Crush
11-10-2005, 05:59 PM
Is it possible the flapper is stuck open or broke in some way?

11-10-2005, 06:02 PM
It sounds to me like your WG is partially open. Maybe there is a bend in your WG arm or the actuator is stuck partially open or something.

11-10-2005, 06:06 PM
have you actually pulled the turbo and looked at it? is there a lot of shaft play? i only ask this because you said it seems to have progressivly gotten worse. if your turbo is worn out, you definitely wont spool quickly or make very much boost.

do you think that an oil leak from the turbo would cause the smoke on the intake side? i can see where it would on the exhaust side... but i dont know.

sorry if these are stupid ideas... just tryin to roll thru all of the possibilites


11-11-2005, 12:16 PM
no shaft play... no bent arm... and it still boots the same amount as it did when i first installed it its just later... i'll check for an oil leak but i just encountered another prob i think my radiator is cracked... i replaced the last squeeze clamp with a worm clam thats where i thought it was leaking from.. but it is comming directly under the radiator...only when the system is pressuring down... like after i have just driven it... Back to the exhaust question what kind of results has anyone encountered with the n-1 system. can you actually feel a big difference in spool time and wot power...

11-29-2005, 04:34 PM
Post Update: radiator is fixed i replaced the exhaust mani gasket and the leak is gone. but the car still boost fairly late... it doesn't feel any better????????????????????????????????