I am looking to get my first TGP this summer and was wondering about the sizing and HP of the stock turbo. From what I have found, it seems the stock TGP came with a T25 turbo. I also know during 89/90 GM forced the TGP to be downgraded quite a bit from the original concept car that was in the plans. I believe originally they were going to put a T03 turbo on. I know the transmission in the TGP's stock, isn't the greatest. How big of a turbo would fit and still not completely destroy the trans? has anyone actually upgraded to biger turbos? How much turbo lag did you notice in going from the t25? From what I have read w/ the T25 turbo, there was hardly any lag at all, is that what you all have found?
hey a friend of mine up graded his turbo to a t03 and the tranny has handled it fine... he did notive alittle bit more lagg but he did get a decent increase on hp im not sure of the exacts but its a good diff between the 2 but it does have alittle bit more lagg
The only detectable lag is actually designed into the fueling program.
The TGP trans isn't so great because its soo old. Try pumping 350lb/ft torque through many transmissions only made to hold 400 originally that are now 13 years old and it will probably have the same result.
Don't know of any one who has actually upgraded. You can get to around 250 hp with the stock turbo, and there are mods to up it to 340 with a t3 super 60 wheel. Considering the overdesigned lag elimination and then re engineered lag, a larger turbo shouldn't create too much actual turbo lag.
chris
Easiest way to get rid of the lag- Get a boost controller. Apexi makes the best IMO. Gredy also makes a good one, as well as HKS. But avoid the TurboXs manual controllers. They are overpriced checkvalve types that our cars don't seem to like.
Getting a boost controller takes wastegate control away from the ECM allowing the driver to tune in were the boost opens up.
I've heard of a T28 called a disco potato or something like that on sport compact mag. BUt the car it was on only top at 274hp. SO i don't even know if it is even worse than the T25 the TGP has or flows simmilar. I guess porting and compressor wheel swaps are the only way on the stock TGP turbo. Other than that a t3 or t4/t3hybrid.
The disco potato is a great turbo for small displacement 4cyls, such as Hondas. For our 3.1 the t-25 is actually to small. It spools fast and holds decent PSI, but it doesn't output enough volume. A t4 would probably be optimal, or even a Toyota CT-26.
The Disco Potato is used mostly in the nissan sr20det crowd. The stock turbo on a Bluebird sr20det is a t-25 with almost the exact same a/r ratios as we have. I know because I'm helping my friend put an sr20det into his '91 sentra se-r right now. Anyways, it's been said that due to the dual ball-bearing setup that the turbo can carry that engine all the way to redline (7500 rpms) where as the T-25 had a drastic drop-off at around 6000. What I'm trying to say is that I love the way our T-25 spools but it's just not happy at higher boost levels, hence why Jeff M's chip only runs 11-12 psi. The Disco Potato on the other hand is very happy around 15 psi so it would still max out our 2 bar map sensor. I've look extensively at this turbo and it would be the ideal direct replacement turbo. From what I've seen it would be a drop in replacement after clocking in correctly and getting the wastegate acutator on. The only problem with the Disco Potato is that it is a dual ball-bearing turbo so it has a $1600 price tag!!
Now, I agree that the Disco Potato is still to small of a turbo for us, but it is probably the best(most efficient) drop in replacement we could get. Plus, it's a GT-28R(dual ball-bearing T-28)...so at least it's a step in the right direction for someone who doesn't want to fabricate anything.
I scanned the compressor flow map, because I couldn't find it on the garrett website. Here it is for anyone that wants to run some numbers on our engine and see how they turn out on this map.
http://fp.enter.net/~nicolette/images/turboGP/gt28rflow.jpg
Also, here's a couple of comparison pics between the Disco Potato and a t25.
http://fp.enter.net/~nicolette/images/turboGP/gt28Rvst25.jpg
http://www.atpturbo.com/turbopiping/turboinfo/GTLineUp/GTLineup.asp
heres some info. I also found it there for almost $800 . I think the other upgreades for this turbo are perfect for the TGP engine.
I've heard of people doing T25/T3 hybrid turbos.
The T28 is actually a T3 in T25 housings, but you still need to deal with fuel and knock retard. :fadein: :drinking: :drinking: :shocked!:
Fuel and knock...well I got the knock part by smothing the C.C., pistons, and premium fuel all the way. Fuel... well I'll see what the A/F ratio meter tells me. Prob an improvemet over the stock rich condition. Less power used to spool the turbo = more useable power. :wink:
I do agree the DP could be a good upgrade, but it depends on what you are going for power wise. The DP is quite happy to boost, but in the case of the TGP, it needs to push more volume. If you are looking for much over 280hp at the wheels, you will need something bigger. The T-25 and Even the DP don't have the volume, and velosity just wont cut it.
The rating you need to look for isn't PSI or volume, its pounds/min. This accounts for density and volume.