No boost till 3rd gear

[XtremeDrag]

I am new to this forum and but i am not new to DSM's

I have a big turbo 1990 Talon that makes pleant of HP but is pretty much usless. I am not a shop owner nor do i work on cars for a living. i just do it for fun so i pretty much figure out things as i go. My problem is that the car doesent make and reasonable boost till 3rd gear. 3rd and 4th gear the car pulls like a raped ape but the trouble is the car is so slow in first and second gear that in the quarter mile i can bareley get the car to pull through 3rd gear and never have the chance to throw 4th

 

[Black Venom]

More information on your setup would help us diagnose your problem.
Thanks

 

[boosted-dsm]

i kinda had this prob. with my old GST ... but it was the guage.. would spike at 0psi in first and hit about 5psi in second.. and 3rd,4th,5th... work fine.. wasnt sure if was a boost leak or just #### up on the guage.. it was strange ### i could feel the car pulling but ya never showed.. in those gears.

not sure if this has to do with eachother.. but it reminded me of it.. thought id throw it in if it helpd any.

 

[92awddsm]

I am new to this forum and but i am not new to DSM's

I have a big turbo 1990 Talon that makes pleant of HP but is pretty much usless. I am not a shop owner nor do i work on cars for a living. i just do it for fun so i pretty much figure out things as i go. My problem is that the car doesent make and reasonable boost till 3rd gear. 3rd and 4th gear the car pulls like a raped ape but the trouble is the car is so slow in first and second gear that in the quarter mile i can bareley get the car to pull through 3rd gear and never have the chance to throw 4th

Fill out your vehicle profile. Your idea of a big turbo and mine might be different. Lots of people think a 20g is big.

 

[Jeff822]

Wouldnt hurt to do a boost leak test just to make sure your getting the most power out of the car.

 

[XtremeDrag]

The car is a 2.0 with a GT42 .. hits about 10psi in 2nd and the whole 29psi in 3rd and 4th

the car has no boost leaks i tested that allready.. im not sure how the evos are keeping boost but i would sure like to know. total timing is at 14degrees but ramps down from about 30

here is a pic of the car when we were building it

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[Black Venom]

I was afraid he was going to say that. Nice setup, Use the nitrous to spool it.
Sorry I can't give much more help, does tuning permit more timing?

Evo's have a better head design.

 

[XtremeDrag]

i do want to spray it but i am still tring to dial in the car and get use to it.. should i be throwing more timming at it in lower gears?

 

[Black Venom]

Push as much timing possible before knocking, Basically just bump up the timing in the midrange-peak torque and see if the spooling improves. It should improve some, but your not going to get alot outta that turbo in the lower gears. IMO

 

[92awddsm]

Im guessing that full spool is somewhere around 52-5500 in 3rd? Are you able to spool it off the line using a 2step? if so, try that and using nlts for 2nd so boost doesnt fall off during the gear change. I would also try pulling some fuel out of the mid range and see if that helps spool.

A turbo that large usually doesnt like to spool in 1st or 2nd because the rpm's go by so fast. I personally would spray it using a pressure switch that turns off around 15psi.

 

[andymoraitis]

The general rule is basically what Keith was talking about in the post above. The load on the motor in 1st and 2nd gear is light due to the amount of torque multiplication in the gearing. As the gears rise numerically, load on the motor increases. 10 psi isn't much and I would expect you to build more boost in 2nd than 1st.

Nice looking setup by the way.

Andy

 

[andymoraitis]

Push as much timing possible before knocking, Basically just bump up the timing in the midrange-peak torque and see if the spooling improves. It should improve some, but your not going to get alot outta that turbo in the lower gears. IMO

Timing will increase the sensation of torque but it does NOT help spool in the least. If anything, lower timing works better since it generates more heat by slowing the exhaust pulse, BUT it makes the motor feel like a slug until the boost comes online. I'd leave that alone and work in an entirely different direction.

One of our wisemen (Luke - GVR5492) taught me a neat trick about using very lean A/F's to generate faster spool. This is something you'll need to play with but here's the basic summary from one his PM's to me on the topic:

"My turbo reaches full boost around 3900 rpms, before I did anything to improve the spool it was around 4300rpms. My A/F from boost threshold to full boost is what most people would consider very lean, it starts around 14:1 and tapers to 11.5:1. So at 10 psi A/F is about 13:1. I gained at least 400 rpms by doing this with no negative affects so far, and it's been over a year. Retarding ignition timing in the same RPM range will increase egt's and give a slightly improved spool, but the loss in torque is usually more noticeable than the increase in boost response. I usually advance the ignition timing as much as possible in that range to increase torque so it "feels" like the turbo is spooling quicker. Playing with the intake cam gear almost always gives a better spool, but it also hurts the top end. Anything you can do to increase the heat in the exhaust manifold and turbine housing will help. Have you considered a heat wrap or ceramic coatings?"

There's some good information in there. Play around with your A/F and see if that will help you build a bit more boost on the low end.

Keep us posted,

Andy

 

[Black Venom]

I appologize for giving atleast some correct tuning advise, but with the wrong stated outcome.

With the increased midrange torque before boost, it will only get to boost faster. It won't boost at a lower rpm.


I would be very weary on how much timing, or lean you want to go with the nitrous to come.

 

[andymoraitis]

I appologize for giving atleast some correct tuning advise, but with the wrong stated outcome.

Don't sweat it. This is a common misconception and I used to think the same thing. Now you know differently.

A/F seems to have a great effect in generating spool, so I'd leave the timing ramp at stock levels for the onset of WOT and tweak A/F to see what happens. Of course lower peak timing is still desirable on a built motor since it will allow for more boost on pump gas, but with the excess heat this generates, I wouldn't deviate much from stock unless forged internals were installed.

For the original poster: I would try this before spraying to see how much improvement can be made before resorting to nitrous.

 

[SBstar]

How is your motor built? It takes alot to spool a big turbo like that and getting everything you can out of the engine first is a good idea, I would assume you already know that though and have appropriately built the head and block. If you are who I think you are (saw you at the shootout) your running the AEM EMS correct? I would assume your running racing fuel as well.

 

[olmytsi]

Were you in Norwalk? I remember a black 1g with that setup that woke me up on saturday morning doing pulls at like 7 am

A gt42r is pretty much a nitrous turbo when used on a small displacement engine.

 

[SBstar]

It does indeed look like that guy.

 

[XtremeDrag]

yeah that was me running the car outside of the track.. sorry for waking everybody up.. that was a 2nd and 3rd gear pull and it feels insane.. but i guess im just gonna have to spray it and see what happens.. it just blew my mind seeing thoues evos going as fast as they were without spray.. and i think they were 2liters also. just think mabey i should have the car tuned by AMS or something

BTW the block and head are built and yes its on a AEM EMS and the car is allways on c16

 

[SBstar]

Yeah if you can't get the tuning figured out, definately go to somone to have it tuned professionally. Probably a good idea with a setup like that anyways. You shouldn't have to spray so I would say a good tune would get you there. Also don't forget to get a roll cage once you do. You'll be needing it!