Hi all,

I am going to be doing my first attempt at turbocharging this winter on my l98 tpi (88 GTA) @ around 4-5 psi. i have been reading posts for 3 days now and havn't found the answer to my questions, so i hope either you can help me or direct me to the thread i must have missed. i also might really be overthinking this, so let me know if i'm being retarded.

1. applying positive pressure to the engine negates vacuum, correct? if that is the case, what are all of you doing to maintain vacuum to your cruise control, brake booster, heater controls, evap canister, etc? The only posts i have seen skirt this issue are ones stating you need to put a check valve inline with the pcv valve or the crank case will get pressurized.

2. firebird owners... how are your underhood temperatures? i have issues with my N/A engine gettin rid of the heat on a hot day... what mods have you done to alleviate this with a turbo and an extra several feet of exhaust pipe under there? i'm tempted to go with an sts type setup as a first attempt due to how much less it costs and the heat issue.



thanks all,

Thunder

 

if u are going to only run 4-5 psi why bother turbocharging your car...total waste imo.....

1. I run no pcv, manual brakes, no AC and no power steering.

2 turbos make alot of heat no going around that. use a cowl hood.

 

because i have never run a turbo before, and 5 psi will be a good starting point to get the bugs worked out so i don't detonate my engine. once i get all the kinks and tuning worked out i can crank the psi

I run power brakes, ac and power steering... i'm not making an all out drag car, i'm making a powerful fun car that can do a quarter in the mid to low 12s. i like having a comfortable fast ride... ac is awesome in the summer and things like cruise control keep me out of jail.

what size cowl do you recommend? maybe a ram air hood with the vents opened up?

 

Everything will still work. While cruising the motor will still make vacuum. As far as cooling, upgrade your radiator, run dual fans, use exhaust wrap and a Turbo blanket. On a stock motor you can run 8psi, without a problem. You could run a PCV valve from a syclone, or run breathers on both valve covers.

Ray

 

excellent.. thats what i was looking for. so at the 5-8 psi i will be running this at standard operating levels i will still have enough vacuum to keep my everything working... very handy. at what psi level do i have to worry about not having enough vacuum to keep things working correctly?

 

You can run as much boost as you want, and all the vacuum stuff will still work. The only time you will get boost is roughly 1/2 throttle and more. I have the pcv running to my air filter, and a breather on the other cover. You could just run a couple breathers instead. The biggest thing is fitting it somewhere and fueling it.

 

i guess that explains why its not mentioned anywhere... i was just overthinking it. I just figured if the intake was pressurized that nothing vacuum related would function right.

 

First off, their is nothing wrong with 'only' running 5 pounds. for a street car that is more than enough to have fun with, not everyone can afford to drop $30,000 into an engine that will hold 80psi making 2000hp...

What fast82 said is true. Under most normal driving circumstances (unless you have a super small turbo) you will not be under boost. A good size vac reserve canister and a check valve inline and your good to go.

You will definately need to do something about the heat, a turbo is going to dump alot of heat in there. wrapping it and even a couple of shields will help but you will probably be best off with a cowl hood.

 

thanks again for the advice... thats easy to do and doesn't cost squat. i am very tempted to do the rear turbo setup for my first attempt... its 10x easier and it doesn't require extra underhood cooling. (i know that is a much debated issue, and i understand the underhood setup is far more efficient... but frankly i'm not made of cash, and don't have a machine shop to bend pipes. I like the fact that i can do the whole sts type system for under $1k.)

two additional questions:

1. i have a line on 2 turbos.. holset h2d and h2c and its a damn good price. would these feed my 5.7 alright?

2. I have a holley afpr... does this regulator react correctly to boost? it obviously can't be put in the vacuum isolation setup or it wouldn't work right. here is the link: http://store.summitracing.com/partde...5&autoview=sku


thanks everyone... i really appreciate the input

 

You have to start some where and 5 PSI is a good starting point. The great thing about turbo setups is you can up the boost with the wastegate later on and add better fuel if it needs it (along with more timing).

Boost is boost. That is, positive pressure. From 0 PSI to 5 PSI you will have 0 vacuum. Use check valves on pressure sensitive items (brakes, CCP, etc). When you are under moderate to heavy throttle (boost) then you will not be "cruising" or "on the brakes hard".

1) Yes, either the H2D or H2C would work for a 5.7 liter depending on the mods. The H2D should flow in the 600-650 BHP range and the H2C in the 500 BHP range depending on the wheel that is in them.

2) no idea on the Holley AFPR. Most AFPR will do 1:1 boost PSI:fuel PSI.

 

1. sweet, because i'm scoring both for $200. i'm thinking thats a good price?

2. according to the specs its Boost/Vacuum Rise Ratio: 1:1 so i think i'm good

 

$100 a piece is good assuming they are usable. Do you know what the markings are on the turbines. You will want a 16 or 19.

It sounds like that regulator will work assuming you do all your additional fuel through the ECM (and bigger injectors) or add a Hobbs switch turning on a Nitrous Fuel solenoid.

 

i currently have 24lb bosch type III injectors.. 2lb over factory and far more efficient. how many psi do u think i might be able to get away with (from the turbo) with just increasing the fuel pressure and metering in the ecm?

that hobbs switch + no2 fuel selenoid idea sounds interesting... do you have any configuration examples? wouldn't maybe using the 9th injector tied to the hobbs switch be a good way to add the extra fuel?