Now that Holley has acquired STS, has anybody considered using the STS kit? When I had my C5 and developed the TT kit for it, STS was making some headway back in 2005-2007. I was very critical of the kit because it wasn't on par with my TTi and PTK twin turbo kits as STS would make claims to produce the same hp. It never did simply because of the remote location and thermal efficiencies lost with the turbine being so far down stream from the hot exhaust gasses that are needed to help spool the turbo. By time the AR was reduced to help with spool it would end up choking the upper hp limits. I went with a larger AR (my TT C5 was in Vette Mag 2x) and sized them so that the low boost threshold or spool started to occur at 2600 rpms and reached full spool at 3200 rpms. This worked great on the street because I could sput around shifting under 2500 rpms in traffic and have plenty of power because it was still a V8...not some poochy 8:1 CR 6 cylinder so there really isn't the lag with a V8 that people complained about on other turbo setups. There was just V8 power and then boost. Compared to my first twin turbo kit which at a T285flange, the turbos would spool at 1800 rpms and it hit like a shot of NOS and then choked off at 5500 rpms. That kit got revised to use a T3/T4 flange. The setup I ended up with just used a T4 flange and produced 850/804 whp/tq at 18# on 100 octane, it was useless so I would run it at 590-600 rwhp on 91 octane. Even at the power level with 335 Proxes out back it I still couldn't stand or go WOT until shifting into 4th gear. I tried many different boost levels and settled for 9# boost for the street. I tried 14# at 745 rwhp and it was out of control, the 850 was just done for a dyno run for the magazine.

However in looking at the STS for a Thirdgen, there could be some modest performance gains for the price that might be appealing. A friend of mine who ran a 9.8 sec 1/4 mile on a 346cid C5, 17" DR on back and an M6 tranny later decided to go with a 427cid. He couldn't get the same time with the same tires as it made a lot more tq than the 346 cid and was much more difficult to launch. Point being that like the LTR/SLP combos when compared to a FIRST or HSR, the tq is hard to put to the ground on regular street tires with the TPI LTR and better with the FIRST/HSR/TPiS, without the traction control new vehicles have it is difficult to launch without the proper tires and setups like the TPI/SLP runners seem to have traction issues down low. Where I'm going with this is the stock TPI makes plenty of tq to get the car moving.

I was thinking since the STS doesn't really spool until 3200 rpms, and the TPI 350 makes plenty of tq to get moving, if the STS spools at 3200 it should supply good boost into the mid/upper rpms where the TPI suffers.

The STS goes in place of the rear muffler. If it is good for 10-12# boost that should make some decent performance gains on a stock TPI with headers.

Thoughts?

https://www.holley.com/products/turb.../parts/STS1001

 

I installed quite a few STS kits back in the day on C5s and LS 4thgen fbodys. Don't see why it'd be much different than a 4thgen and I'd think it would work pretty well with the 3rdgen.

 

Does the pic in the lower left corner (click on link) look like a Thirdgen?
https://documents.holley.com/199r11607.pdf

 

I had built my own remote turbo setup. My 1991 Z28 bone stock with 305 tpi. It worked fantastic. Trick is to get the oil drain system worked out right so it doesnt leak into the exhaust housing and smoke. It helps to make a small reservoir to drain into and scavenge pump from that

keep the exhaust pipe size relatively small depending on how big turbo you go. I ran a T4 70mm budget turbo with 65/74 mm turbine. P trim basically they used to call them.

9 psi really woke the car up. You should wrap exhaust. Mine was 2 1/4” pipe to turbo. Left the cat on it and it worked well. 2 psi at almost half throttle at 2400-2500 rpm. It spooled well. Took cat off and spool sucked. Had to go down to .68 housing vs .96. It was still touch laggy but doable. At the track it would make 5 psi in first gear and 9 after the shift in 2nd. Car reallly needed 2500 rpm stall to light that turbo off fast from a dig. Street rolls it was fine.

 

Orr- you have had like every setup lol. Cool stuff. I'm surprised that the turbo spooled slower with the cat off, must have cooled down the exhaust gases enough without the cat? Only thing I can think of really that would cause a slower spool up with all else being the same.

 

Yup my guess is it was a heater of the exhaust. And might have created a tiny but more drive pressure. But if i would have wrapped the exhaust I’m sure it would have held on to heat longer and would have spooled better. It wasn’t bad however. A converter would have solved that problem

on a tpi car having it spool under 2800-3000 isnt really necessary or desirable imo. There’s already alot of cylinder pressure at this point because peak trq is there. Spooling here and makin boost over 3000 will help top end pick up and extend beyond tpi limit of typical 4500 rpm

 

4th gen.

 

It is a 4th gen but 4th gens are basically a 3rd gen rear back half. Fuel tank and all the rearend and suspension are all the same an interchangeable. Definitely wouldn't be an issue running a sts kit on it. The biggest downside is having to use a scavenger pump.

 

Rear end is not the same.

 

they still are interchangeable regarding suspension parts and mounting points

 

Indeed they are. However, that is not what the person whom I quoted, said. They said: "all the rearend and suspension are all the same an interchangeable"

Someone reading this could be misled and make the same mistake that I made, nearly 30 years ago, by sticking a 4th gen rear into a 3rd gen car, lowering it down to the ground and.....whoops....that sure looks dumb. Because it's not "all the same". The 4th gen rear, while it will bolt into a 3rd gen car, is about 4" wider than the 3rd gen rear, making for quite a '70's hot rodder look.

 

I have a 4th gen rear in my car, which is great when running 4th gen wheels. When I tried to mount 10" slicks that's when it became an issue with the offset. Lesson learned.

-- Joe