Impala Balko

I want to attempt to build a remote mount turbo setup for my bolt on 94 6 speed coupe. I just purchased a 76mm On 3 Performance Turbo second hand for a reasonable price I am looking to mount it right behind the rear differential and I am looking to mount the intercooler in the back in place of the spare tire. Where are some good places to get compressed air pipe. Does this have to be aluminum and what diameter does it need to be? And how big of waste gate do I need? Is it possible to run a dedicated oil system for just the turbo? Also what should I use for a scavenge pump? And do I need to do a catch can as well? What size injectors should I be looking into purchasing as well as fuel pump as well?

mnstrlt1

76mm is healthy, however, I've heard some mixed responses about the "On 3" turbochargers. Most people ditch the stock turbo (from the kit) in favor of a better brand. Keep that in mind, when considering the health of the turbo you have.

With that said, "Raptor" (forum member) collaborated with STS Turbos (remote mount company) to develop a rear-mount turbo for these c4's. If you do a search, you'll see a well documented thread (with photos).

Rear mounted intercooler isn't necessarily (or ideal) for a rear mount kit. The length of the return pipe Is long enough to have an intercooler effect.

The Raptor kit using the oil feed from the engine, with a return pump to feed the turbo. Stainless steel is usually used for the hot side, and alloy is used for the compressed-air side (cold side).

Injectors and tuning will depend on the expected horsepower and boost you run. Generally speaking, a 255lph in -tank (or larger) with 60# injectors will get it done (roughly 500-650ish rwhp).

Impala Balko

Thanks for the information. .. I knew that the turbo that I selected was a knock off brand, this is just a sort of budget build to kind of test the waters of the whole turbo thing/ see how much power I can get out of the stock motor with it still being safe and reliable. If I like it I plan on building a ***** out turbo motor.

mnstrlt1

A general rule of thumb is to keep boost around 6-8psi on a stock motor. However, I've run 9psi on my 93' stock long block with a vortech t-trim without issues. The key to longevity is to avoid constant abusive driving (in boost). My 93' was my daily driver, and had been supercharged for 2-3 years without ill effects. I've seen guys run 10psi on stock long blocks, and more might be possible. Tune is critical, fuel delivery, and driving manors.

Impala Balko

As far as tuning was it tough to find a place to tune it properly or was it easy to get it dialed in

mnstrlt1

Turbo cars are tougher to tune than supercharged cars (at least centrifugal superchargers- because the boost delivery is relatively predictable and linear).

if you have a 93' and earlier, it's going to be slightly time consuming (it's a chip that has to be pulled, burned, and re-installed). There are a few companies that offer hardware that allows the computer to be tuned "live" (like modern cars). If you have a 94' and newer c4, than the computer can be tuned "live". It will require the hardware to transfer files into the computer.

some companies to talk to about turbo charging and tuning would be;

Raptor LLC (joint partner with STS turbos). This would be the most logical source, since they have already made the kit for these cars and would give you the most sound advise.

Blower Works, Gregg is still very active in the corvette community, and he should be a wealth of knowledge regarding a "base" tune and data logging. Not to mention fuel needs, and other details.

TPIS.com, these guys are very active in the earlier GM cars and should be able to tune your car (mail-order, via mailing you a chip or tune) or tuning the car live at their facility.

FastChip, Ed Wright has been recommended by others. I haven't had any direct experience with him, but he's a credible source.

PCM For LESS, these guys are still very active in the earlier GM community, and can also lead you in the right direction.

Gmtuners.com, also a very knowledge source for earlier GM cars, and he's built a few turbo GM engines in order vehicles using GM cars.

There should be some others, but this will give you a general idea of who is out there and the list should also cover most geographic areas of the US.

Orr89rocz

Generally run alittle smaller exhaust side with the remote stuff. Use alot of wrap for heat management. Want hot exhaust all way back.

Cold side piping doesnt need to be aluminum if you want to work with steel exhaust tubing but aluminum is lighter and runs cooler.

Can do self contained oil system but would need cooler and fan back there to keep things happy. Oil will get hot and cook without it after some time.

Need scavenge pump either way so best i have heard and currently run myself is turbowerx exa pump. Pricey but suppose to handle the heat and long duty cycles. Easy to mount and run. I run my relay trigger to fuel pump relay wire which is on only while motor runs


What motor is this going on? Want low boost control try for a 44-46mm gate. A 38-40 would work tho. For injectors that depends on motor and hp and even fuel size. What efi system will control this?

Impala Balko

the turbo setup will be going on the stock motor for now, and can the stock computer be tuned to run with a turbo setup

mnstrlt1

The stock computer can handle it. Some "pre historic" methods involve an FMU (boost pressure based fuel management unit- I do not recommend it over a tune), and an ignition box to retard timing with boost reference (i.e. MSD 6-BTM, again not the "idea" setup). However, on a low-boost application and for a budget oriented situation, this would work (let's say 5-7psi boost). anything more than that, I'd switch to injectors, pump, and tune the actual vehicle's computer.

Both the chip based computer, as well as the 94' and newer cars can be tuned to support a boost application. Unless you need absolute, precise control (exceeding the factory computer's perimeters), in which case, you're looking at thousands for a proper stand-alone computer. You will likely loose some functions in the dash going this direction.

Orr89rocz

If they have a 2 bar program for the 94 you can tune it. Else convert to obd2 24x sfi from eficonnection and run a 2 bar ls1 type program. More ppl out there capable of tuning those

Impala Balko

I do want to do a 24x setup on my next motor but I was hoping to avoid doing that right now because it will delay the completion of this build

SinisterC6

I think that it's awesome your taking this project on and will love the feeling a turbocharged Corvette provides. Is there any way to mount an intercooler up front? The long charge piping will do some cooling and the intercooler will provide the rest. I fear if you mounted the intercooler out back anything the intercooler does will be lost through the charge piping and you would end up with high IATs

mnstrlt1

I'm certain I read in one of the threads (on this forum) that Raptor kept an eye on intake air temps. This would be the reason to also use aluminum (helps with heat). I would venture to guess that up-to 10psi, you'd be ok without a traditional intercooler. I ran 9psi on my Vortech (the blower is much closer to the throttle body in that scenario) without any tuning issues or need for an intercooler. Centrifugal superchargers and turbochargers are pretty efficient.

Packaging a decent sized front-mount intercooler in a corvette will prove to be a little challenging. For instance, the procharger intercoolers (offered with their supercharger kits) have proven to be too small to be efficient for an extended period time. This is also why Blowerworks offers methanol injection systems as a form of intercooling. It's easier to package and is pretty efficient (I currently run one).

24x swap would be great, but it isn't cheap. It's almost as much as a Big Stuff, FAST, ACCEL stand alone. Most c5/c6 boosted corvettes switch to a "speed density" tune rather than a MAF tune.

Without getting into too much detail about the computers offered in corvettes and if they are/are not compatible with 2-3 bar MAP sensors, I wanted to mention that nearly all supercharger kits RETAIN the stock 1-bar MAP sensor. Fuel and timing can be tuned for a turbo car without having to step to a 2-3 bar map sensor as well (basically, the corvette factory computer wont recognize a 2 or 3 bar map sensor anyway, you'd have to find a computer out of a different GM vehicle and the tune it to make it work- this get's involved and you lose some factory functions).

stay simple initially, with moderate boost. You wont need to worry about 2 or 3 bar MAP sensors, stand alone computers, or a 24x swaps until you decide to go for more power.

Orr89rocz

If you buy just the ring and cover with sensors and do your own harness its significantly cheaper than aftermarket stuff. And 24x is speed density. You delete the maf in the tune.

Orr89rocz

If you buy just the ring and cover with sensors and do your own harness its significantly cheaper than aftermarket stuff. And 24x is speed density. You delete the maf in the tune.

BlowerWorks

Hi Guys ! I have 2 BAR tunes for the 1990 thru '96. Not needed on the 1986 thru 1989 as the MAF's I have can handle 1000 HP.
greg

rhanselman

Yes, temps were monitored and it was determined that the LT1 didn't need an IC. My LT1 car is over 600 RWHP without an IC... My LT-5 Remote Mount Twin Turbo has an IC just because of the LT5's open deck config.

Cheers,
Ron

rhanselman

BTW - Corey Henderson of Henderson Performance is installing Raptor Remote Mount C4 Turbo Systems just north of San Antonio. I think you can get a single turbo system installed and tuned for around $5k.

Impala Balko

Do I just get the oil for the oil feed line directly from the pan or do I plumb it some where else. I ask this because I found a guide for building remote mount turbo setups and they said for LT1's "On the LT1, you will run the feed from the ¼” NPT port above the oil filter" Does anyone have a picture of this area because I am baffled

rhanselman

I can save you the money and tell you right now what it will do stock: 407 RWHP & 437 RWTQ w/single rear mount turbo @ 8 PSI. Stock 1995 ECM with tune.

I can also tell you that the same turbo on the built 9.5:1 forged engine will do: 600+ RWHP at 15 PSI. Upgraded Fuel system was also required...