stock turbos...running 2 on a 5.slow...couple questions

[il_wolf_li]

Just a few questions about stock '86-'87 GN turbos, how fast have people gone with the stock turbos of that year? I ran 2 IHI turbos off the '87-88 turbocoupes last year and it was a pretty fun little setup but I am looking to run a lot faster. Is there any little things (dont cost a lot) that I can do to my stock GN turbos to improve them, I hear the wastegates are a problem, something about grinding on a little or welding that will improve them. I am shooting for some 9 second action with a couple stocker turbos and a healthy 5.0.

Thanks, Brian

 

[Turbostangman]

I can't believe your not asking me about this.

 

[il_wolf_li]

turbostangman, I believe I posted a question about this directed at you a while back on TM.com but you didn't see it. Thought I would just post over here on the turbobuick board and see what they think.
But how did you like the GN turbos over the T25's you were running? I know you werent getting full boost till like 3300-3500rpm with the GN's. My intake, heads and headers should flow a little better than yours so I am hoping that will bring the spool up time down a little (if i am thinking about flow properly). I remember that your shorblock had a ton of blow by and my shortblock has just been freshened and assembling the motor this week. You went 10.7's with a tired motor so I am hoping with more boost than you, a fresh bottom end and some more supporting equipment that I can crack a 9 sec. pass. Also, how was the car on the street with the little bit more lag from the larger turbos? Another thing is are these turbos larger than the turbocoupe turbos, I know mine say .63/.60 on them and I thought they were almost T3/T4 hybrids....????

Thanks,
Brian

 

[Turbostangman]

I thought I replied to that thread and never saw you post back.

Well as far as the the GN's versus the T-25s, no comparison. Yes they were a bit laggy until I got the C-4 and good converter. But the top end pull was a ton better. Part of the response problem was the converter and the AOD.

With the looser converter and C-4, boost was almost instantanious. I could come on the throttle hard at 1,500RPM in 3rd and the converter would jump to 3,200RPM and spool the turbos to 7psi instantly. After that it was a matter of no time and 12-13psi would be right there.

Think about it. To go from High 11.7s to 11.2s with just some new turbos, IC, and Intake. And then from 11.2s to 10.7-.8's with nothing but a tranny change is a huge couple of jumps. 1/2 a second each round of mods. Over 1 full second in all.

It's like all things, the ENTIRE combo makes it either good, or GREAT!!

Well, there are a lot of things that effect how rapidly a turbo spools. If a fast response is what you're looking for then bottom end power production via compression and torque is the recipe. As yours sits, ring seal will be an advantage over my tired old motor.

I'm not sure if stock GN turbos would have 9s in them. I kinda felt that I would have gotten just over 130MPH had my motor been fresh, but not much more. Mid 10s deffinately, Low 10s a good possibility. 9s may be a little bit of a stretch.

Try it and see!! There are always upgrades available!!

 

[JDEstill]

well, first off, just how much boost are you planning on running? Remember, there is more to sizing than just flow, pressure is just as important. If you are going to be running big boost, the stock GN turbo may not be your best choice, even if the acfm it is pulling is within its rated capacity.

re: the wastegate thing, the turbine housing has an integral wastegate. Guys that have had problems with boost creep have sometimes opened up the wastegate hole to help it flow more. If boost creep isn't a problem with your setup, no need to do this.

Give me an idea of your max rpm, the boost level you want, or the flywheel hp you are looking for, whether you are intercooled or not, and I'll give you a ballpark answer to the suitability of the GN turbos.

John

 

[turbonatr]

A stock GN turbo can be taken into the 11s on a Turbo Regal. A pair of them on a TR is more than enough for a 10 second car. 9s may be pushing them in a V8 powered car. You are much better off with a pair of TA49s or similar.

 

[il_wolf_li]

Turbostangman, thanks for the info., I know BSharrer ran 9.8's with a couple .60/.63 T3's but he was pushing them hard and kept blowing the seals I believe. I remember reading your site a bunch when I realized how inexpensive I could get these GN turbos and your combonation screamed. One of the main things I always remembered about your setup was the decent amount of lag but sounds like the C4 fixed that problem, but lag is a blessing in disquise when running on street tires. Do you run street tires or drag radials around on the street? What was the fastest you have spun your tires at from a roll, mine was about 60mph with my old TT kit. I was getting full boost with that kit at 2400rpm with the IHI turbos and that would just annialate the tires so I would like to be around 3000-3200rpm which is what you said you are at.

JDEstill, I really don't know how much boost I am going to run at the moment, pretty much as much boost as it takes to run the ET I want, I don't really go by hp, I am more into the proven times it will run (unlike supras ) . But here is the boost I think I am going to have to run in order to hit these times:
10psi- high high 10's on slicks
13psi- mid 10's on slicks
16-18psi- high 9's
-It will have a decent sized Intercooler on it
-shift no higher than 6000rpm, more around 5800rpm
Here at our track my friend ran 10.91@125 with 13lbs of boost from small .48/.60 IHI turbos on his completely stock '115k mile' longblock (no porting, didnt even remove lower intake).

turbonatr, yeah, those would probably work better but I have $160 and some labor time into 2 '87 GN turbos so I am going to use these for now, I will be upgrading down the road.

little info on my setup:
The heads I will be running are Aluminum Twisted Wedges that have been CnC 'stage 3 ported' which flow 287/204@.500 lift and 314/216@.600 lift, I will be running the F303 cam (.512/.288). GT40 intake with the lower port matched to the heads, 70mm T/B, flipped BBK shorties, 42lb inj., 255 intanke, etc.

Brian

 

[turbonatr]

I would go with a bigger injector than 42lb./hr if you plan on 9s.

 

[il_wolf_li]

I had a thread on TM.com about 9's and 42lb inj. and I got the thumbs up from about everyone. They all thought that it would just be enough to crack a 9. Oh yeah, I am only going to try 1 or 2 times for this magical 9 second pass since my shortblock is a stock block.

Brian

 

[turbonatr]

I'm a member on TM.com, too. You think "just about enough" is safe? I realize you're only looking for a couple 9 second passes, but keep in mind there is going to be a tuning process involved. Being that you are running the stock block, I would think the last thing you would want is an inadequate fuel system (at least injector wise). Remember, if you waste an engine, all the contaminents in the oil go right through the center sections of the turbos, not to mention there is the possibility of ruining the heads. Ever see piston chunks melted to the combustion chambers of an aluminum head? It's ugly.

Good luck.

 

[JDEstill]

il_wolf_li, I only checked things at 18 psi boost, since if your parts are good for that they'll be good for lower boost levels too.

Turbos - looks like two stock GN turbos are pretty well suited for operation on a 302 at 5800 rpm @ 18 psi. Probably not much incentive to to go bigger.

injectors - I'm with the other guys, 42's should end up being right at 100% duty cycle at those conditions, 50's will be a better choice, although the 42's will be good up to 14-15 psi boost.

Whatever the case, at 18 psi you ought to be good for 575-675 hp, depending on how things shake out. Hope that gets the times you are looking for. Sounds like a lot of fun!

John

 

[il_wolf_li]

Yeah I figured I would be running the injectors at 100% duty cycle, right there on the edge. I have a friend that owns a dyno and I would be tuning my car on that for pretty inexpensive since like you said, melted parts aren't cool. I will have to see about the 50lb injectors, those are really spendy compared to the 42's but I will just have to see how my funds look. I guess we will just have to see how this setup runs. If I dont think I can get a 9 second pass I will just keep the setup running high-mid 10's and take it 'somewhat' easy on my shortblock. The main thing is keeping my car together and having fun with it all next summer and terrorizing the crotch rockets. And for the really modded bikes I will get my friend and his Twin T66 351 AC Cobra to take care of them.

JDEstill, thanks for checking that out for me.

Brian

 

[SNEAKY]

Originally posted by il_wolf_li
Turbostangman, thanks for the info., I know BSharrer ran 9.8's with a couple .60/.63 T3's but he was pushing them hard and kept blowing the seals I believe.

yeah bryan was pushing his twins preety freaking hard. he also ran those times with ported windsor senior heads also, and an Ecam without an IC or waterinjections.
as of right now i am finishing up my car on which i am using Forrest's kit that he built. i am hoping to run some low elevens without much trouble. but i am running stock heads and cam on a 8.5:1 compression motor and 42lbs injector. but for now i will not have an IC. i want it too sound like a linlcon and pull like a powerstroke.

i think a couple of stock GN turbos would be pretty good on your set up, but i am with the rest of the guys on the injectors.


GoodLuck

 

[Chuck Leeper]

jector sizing

I just ran some numbers for a "for instance" on this combo.
I assumed the car was at 3200#.
I looked at my history charts, and chose an ET of 9.99. The MPH at 9.99 is near 135.
This info says the FWHP has to be in the 625 area. [John's calcs are right w/ mine]
Given those values, the injectors, at a 90% duty cycle, and a BSFC of .6, must be 52PPH units.
Given the engine is mostly stock, the BSFC is probably worse than .6.. could be near .7.. If so, then the engine has not a chance of survival running at 625HP...
The EGT's will go thru the roof, the piston ring lands will cave in, and could get ugly, real fast!!!

Have fun...

 

[il_wolf_li]

Well my motor isnt really stock, new rings and bearings in the shortblock, CnC ported TFS heads, F303 cam, Ported GT40 lower and a GT40 upper (also have a Cartech upper). But thanks for doing some calculations on my setup for me, I will be second guessing what injectors I will run.

Oh, I just got my car running all motor and best ET was 12.401 letting out (12.40 dial-in) and best MPH was 109.99, best 60ft was a 1.66 on 26x8.5" slicks pulling the left tire 6" off the ground. With more tunning and suspension work it should got 11.9's. The 12.401 pass I trapped at 98mph. I will be back out in a couple weeks to run it out the back door with just me in the car.

Brian

 

[EightSecV6]

We have a stock short block 90 lx with old DFI,TFS Hi ports, solid roller, and PT72 turbo with no wastegate and TH400 that went 9.70s at 140 about 5 years ago, it would only make 18# of boost. We are currently converting it to twin "GN" turbos along with 2 "GN" intercoolers welded together side by side to complete the intercooler and a set of custom headers, looking for mid nines and non existent lag.
Bill

 

[il_wolf_li]

Damn, now that is flying. Happen to have pics of that turbo kit? Still have it around somewhere....for sale?


Brian