Spooling problem

[turbodaniel]

I have a precision 76gtq thats really lagging wondering if this is a common issue for this turbo if not where do i need to look . Did a 0 boost test and that came in at 3000, at 3500 rpm boost is between 1 and 2 lbs the converter is a coan with a 4400 stall. I was told the sprag might be bad... Maybe a converter change or turbo? The engine is a standard stroke 109 with girdle, comp cams 234 ,96lb inj with a good tune.

 

[GNVYUS 1]

3000 zero psi isn't helping, I'd either get that raised from Coan to at least 3600-3800 or contact PTC and just have Dusty help you.

If this isn't a low 9 strip car, you're not going to like the street spool unless you run Nitrous. Why not a Billet 71BB and blow the block in half with that turbo, at least it will spool better?

 

[turbodaniel]

I am calling precision tomorrow and see what my options are i heard changing the exhaust housing might help. i really am not concerned about the street spool just thought there should be more boost at 3500 rpm

 

[turbodaniel]

exhaust housing

i am changing the exhaust housing on my precision 76htq, will there be tuning adjustments that will need to be made or is it just bolt and go? am not that well versed with turbos so i am just trying to gather information

 

[Dusty Bradford]

This is what you will run into with a turbo this large. I'm not sure a housing change will help much. I don't know the specs on your current converter but even if it spools quick it's going to slip if you put mid-low 10 second power to it and shift it under 6k.

A converter can help but a turbo change will help the most. Get something that will better suit the rpm range and e.t goal of the combo.

 

[turbodaniel]

little confused my thinking is you would like to leave the line at 6-8 lbs of boost my car isnt going to do that till 4000-4200 rpm,my thought thats a little high since im shifting at 6200 if it made that at 3600 it would be better use of the power band

 

[jasjamz]

i am changing the exhaust housing on my precision 76htq, will there be tuning adjustments that will need to be made or is it just bolt and go? am not that well versed with turbos so i am just trying to gather information

Give Precision Turbo a call and ask for Patrick Rubio. He will guide you through this issue you are having. It would only confuse you if everyone started making suggestions. He know his stuff and can sum it up in one phone call!

 

[Dusty Bradford]

little confused my thinking is you would like to leave the line at 6-8 lbs of boost my car isnt going to do that till 4000-4200 rpm,my thought thats a little high since im shifting at 6200 if it made that at 3600 it would be better use of the power band

Launch rpm and boost don't really matter. You leave at whatever makes the car happy will get the 60' your looking for. A loose converter will 60' better on lower boost because the rpm is higher. A tight converter will need more boost to achieve the same 60' because the rpm is lower for a given boost level.

 

[bison]

I have merged the 2 threads. They both revolve around the same topic. My advise is to go to a 65 trim turbine with a .63 ex housing. A 66 or 67 compressor. Spoolup will be better. A housing swap on a hpq won't do much at all for spool here.

 

[turbodaniel]

thanks for the good advise

 

[et10sec]

i have a .63 housing i took off a gtq76 for sale, let me know!! ed

 

[WIKEDV6]

76 GTQ seems too big for for a stock stroke 109...... I would go to a smaller turbo!

Just my $.02
Prasad

 

[jasjamz]

What fuel do you run? I remember Street Performance, a local TB shop that closed up a while back had a 76 GTQ on a car with nitrous to spool it. 109, main caps, champion aluminum heads, small hydraulic roller, FAST, and a th400. High 9 second car over and over again. This was back in like 2003-2004.

 

[WIKEDV6]

What fuel do you run? I remember Street Performance, a local TB shop that closed up a while back had a 76 GTQ on a car with nitrous to spool it. 109, main caps, champion aluminum heads, small hydraulic roller, FAST, and a th400. High 9 second car over and over again. This was back in like 2003-2004.

Yep, I remember that....I still know where that car is too with a different power train in it...lol
You know opinions are like A$$ holes every body has one...I am not an expert in anything, I don't have any actual data from a dyno nor conducted any extensive study like few people here on the board so take it for what it's worth! In my experience, if you want to have fun on the street with a 231-235 cube built engine, I wouldn't run anything bigger than 67/65 we have few running around and they are a lot of fun. You can also try to get away with 67/68 or an old school 70 P trim (76trim). I would stop there. I know the new technology turbos are pretty efficient and spool up pretty quick so that you may be able to get away with more..... It all depends on your combo and tune. My buddy runs a 67/68 on a 235 cube engine and he has a blast with on the street. 10.20@ 133 on Dr radials and E85. Sometimes you need a trans bake will help you spool up a bigger turbo sometime you need to hit it in the a$$ with a 50 shot to get her out the whole if you want to run a huge turbo. We ran a GT42/76 on a production 4.1 ran a 10.009 on Dr radials.....turbo 400 with a T brake netting 1.37 Sixty foot!

We also ran into some boost creep issues with the new technology billet turbos as they are so efficient. It all depends on you waste gate configuration. Once we moved the waste gate to the header below the turbo, the problem was solved.

HTH
Prasad

 

[Bob Davi]

HI,

The title of this thread caught my attention as I recently swapped turbos. I have an 86 T-type stock block, heads, cam, Walbro 255, with a THDP, 60# Siemens, Alky/Razor inj system and a fresh Turbo Tweak chip to match the new setup.. I had a TA-49 and a 9-11 converter. It ran fine although the converter was never what I thought it could be. Anyway, I had been telling my son Iwanterd to upgrade the turbo a little. As a gift, he went and got an 67mm, P-trim E-bay turbo, then sent it to a guy who turned it into a BB with a Precision exhaust. All I know at this point is it's got a BB in one side of it and journal on the other and is a 61 or 63 AR.... that's what my boy told me and I'm having a difficult time contacting the guy who did the swap. It has a 3 bolt flange and the exhaust housing bolted right up to DP.

It runs fine, but I am now experiencing the dreaded "lag"....I did the RPM/1# of boost and it gets to about 27-2800 to make that initial boost. So now I am off to find out what the proper coverter would be for a 90% streetcar. Everyone tells me the right converter makes a night/day difference in these cars.

It runs real nice from what I can tell, but I am no where near an expert on these cars. It seems to be a nice "pull" from 20-22# boost. My Scanmaster showed 810 and zero knock at 22# with Alky set at 6. I was told 22# was still "safe" for the alky on 91 octane. I do have access to 100low lead Avgas, but I want to be safe with the pump gas.

Any advice or "don't do that" is appreciated.

Thanks, Bob 940-902-1266

PS. Anyone seen Dan Brodawski lately



I talked to Dusty yesterday before doing the boost check on the converter; now I have some info for him to work with.