A bigger turbo will make more power than a smaller turbo at the same boost pressure, correct? Ideally I want to stay around 15psi (hoping to keep it together for awhile). Is there a reason I couldn't run a bigger turbo (80 or 88?) and just spool it with nitrous until the boost comes in? If that is an option, does the cylinder pressure increase?

I've read a ton of threads of guys smoking head gaskets at 17-20 psi on these motors. There just isn't enough material between the water jackets and an open deck block. Most are using combinations of stopper gaskets, L19 studs, aftermarket closed deck inserts, o rings, etc. So I am trying to figure out if I can make more power without increasing cylinder pressure. Some of those issues I am sure is due to lack of experience.

My machine shop said they could install "deck stanchions" and would old u to 30psi. I've been around awhile and have never heard of deck stachions? He described it, but I had a hard time visualizing it. He machines some sort of rod above each chamber evidently. Curious if anyone has heard of this?​

 

Thanks for the reply! I sent them an email and waiting on a reply. I ran across a used S366 on Ebay that I got outbid on. I bid 300 on it and it sold for 390 shipped. For that price I'll just buy a new one, if that is what I go with. I was thinking if I find a deal on something, just buy it to fab the system and try it. If it sucks, I'll just swap it out...

 

How much power you want? boost numbers indicate a great number of things but they do not directly correlate to Horsepower, a better breathing motor might need less "boost" to achieve said number, a better breathing motor will also represent a different turbo sizing.

By the numbers you have provided and the turbos you have shown, sounds like 800-900hp? does the stock block represent a problem up there? really don't know them vq37s...

 

More power is increased cylinder pressure. No way around it. Now at peak torque your cylinder pressure is at its highest. But thats relative and increases along with power increase. So you can be proactive and keep peak boost realitively high in rpm. What is high enough depends on the engine.

As for as bigger turbo. Bigger does not mean more efficient. But on average it does. Just depends on wheel technology. You can have a ching chong cheapy make 14 psi and 500hp. You could slap something with the same comp wheel size but better wheel and cover design , and make 100 more hp at same boost and rpm.

An 80 or an 88 on that motor will need more rpm to work. Talking like 10-11 k rpm with the 88.

 

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Thank you sir! Zero chance it'll spin that high, lol. I can go to about 8K safely. I guess I was giving the nitrous too much credit. Seems like most are recommending a 66ish.... wondering if a 76 would work with some n2o help. I will probably at some point reach out to a professional when I purchase, I want to make sure it is efficient and works. The nitrous thing sounds like a no brainer, especially on a little motor. Just not sure how that impacts what changes to the turbo...

 

You really need to sit down and map out your goals before you start buying parts. It sounds like you just want "the most possible" which isn't realistic unless you have extremely deep pockets and are willing to dedicate the car to being a track only thing. You can get the block and heads set up for o rings, increase stud count, partial or full fill on the block; is this meant to be a fast street car or a race car? Getting past 600rwhp on something that light is going to be really unpleasant on the street in the best of conditions with full suspension and extremely sticky, soft tires.

If people are having good luck with 66mm is their power peak less than you want? If you are willing to stack nitrous on top of boost why not use the nitrous to hit your power goal? Supra guys are making over 800 on shelf stock s366. Based on your posts that's more than your block and heads on this platform are capable of withstanding without serious engine work.

A turbo that only lights on NO2 is no fun on the street.

 

I actually have a plan and I've have experience making good power....I'm just new to turbos. The car is a street car that will get drive alot. Occasional track passes and playing on the street. My last car put 700 to the tires.... that would be the goal. If the car can consistently handle that I'm sure I'll turn it up at some point.

The block can handle 1000whp, it has a one piece main cradle and I'm installing studs and forged internals. I've read threads about lifting the heads even using studs, o rings, filling the block and machine deck supports. The heads still lift. So the goal is to run 15-17psi, whatever it makes it makes. I think 600-700 is pretty realistic.

 

The only way to run high boost consistently is a billet block, which is not an option, lol. My machinist builds big hp GTR's and says he has a method to hold 30 psi.... I guess we will see if it works. 28-30 psi would hall the mail for sure...

 

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The lower end can hold 1000whp. Problem is the way the water jackets in the heads are designed there is issues with keeping the heads down with 17-20psi. 800 or 900 would be perfect, realistically probably 700-800 at the flywheel.

Motor will be pretty snappy NA, for a v6 anyway. Stock compression is 11-1 and I'm still going back and forth on what pistons to order. Given the fact that I most likely will not be able to run much more than 15psi... I'm leaning toward running JE 11.5-1 pistons. I'll be running a .020 thicker head gasket and I unshrouded the valves. Havent CC'd them yet but should fall pretty close to stock compression. I'll be on E85 so thinking the higher compression is the right move.

I'm spending a ton of time on the heads and they are looking real good. The factory casting flow pretty good and everything is damn near gasket matched from the factory. It is pig heavy 4k street cruiser...

 

Lag is never a good thing and weight and lag are really not good friends, higher compression should help on spool and off boost response though.
Like it was stated before, run a small hotside, everything pre-turbo should be "small" downpipe the biggest you can fit.
A decent 6766 should give you your desired HP.

 

Thanks for your advise. Couple questions and I think I'm there...

- As you move up to the more expensive turbos, if they are all the same specs what do you gain other than lighter, stronger and better bearings? I'm sure the higher end units spool a little faster but at the end of the day is it worth it on a street car? I'm trying to grasp the performance difference between let's say a VS, BW, Precision or Bullseye? If all 4 were 6766's do they all 4 make the same power at 15psi? The better units just get there faster?

- Can you get too small on the hotside? Should I consider under 2". The factory manifolds are 2.5", does it matter where or how I merge it down as long as it's closer to the manifold? I'll be using a Spintech transition piece to make the merge close to where the stock cats are mounted.

- I should have room for a 4 and maybe even a 5" down pipe since it's in the rear. I would like to use a Borla XR1 muffler on the down pipe and a high flow resonator before the turbo. Trying to tone down the exhaust note as much as possible.

- Charge pipe will probably be a total of 9ft. I dont want to run an intercooler but I need to route to two throttle bodies. If I use a Y in the engine compartment will it matter if one bank has a longer run from the Y? Or do they have to be the same length?

Thanks for your help!

 

Also assuming a T4 flange... divided or no?

 

Given te application and considering that this is just my opinion:

1-Compressor and turbine design might have a great impact on how a unit behaves, depending on certain factors, they would affect both power potential and spool times, a VS might not flow the same as a Precision for example, or it might not spool as easily, like comparing ball bearings vs journal bearings it all depends on what you want and/or are willing to spend.
A 200-250rpms difference in spool might not sound like much but it does help.

2- I would either do 2" to the merge and 2.5" to a t4 (undivided) or two 2" directly to a divided t4 (the use of 2 wastegates should be considered in this scenario); with all the pipes wrapped to help it keep energy and heat.

3-4"- 5" would be ok... being a 5" even better, I dont recommend installing any muffler Before the turbo (did I read that right?) as it could greatly affect spool time and depending on the muffler design it would most probably disintegrate because of the heat and kill the turbo while at it.

4- Considering that the engine uses 2 TBs I would do a merge of them both, simple Y (same lenght because of my OCD) and route the pipe; I would also recommend the use of an intercooler and not just any intecooler, a good unit would be needed, 15-20psi worth of flow in a high efficiency high revving engine can be A-lot heat from a 6766 and considering the "high" CR (11.x:1?) I would say an intecooler is a must.

5-The T4 ar is a critical point, you can improve response with small ar's but affect top end performance where the 6 cylinder shines.

6-Proper oiling of the remote turbo should also be taken into consideration, additional oil pump, coolers etc

 

turbo



1. I will probably start with a lower to mid turbo at first (600-1200ish), give the appliction

2. I'll just run an open T4 flange

3. When I said muffler I meant a straight through design, but I guess even those are too restrictive and will grenade. Assuming a straight thru after the turbo is ok. Any other recommendations to make a quiet exhaust note?

4. With it being rear mounted and on E85 I thought I would be able to eliminate the intercooler, too eliminate piping and increase spool time. If I do run an intercooler it solves my throttle body routing question.

5. I would rather have the extra power on the top end. The chassis and suspension will struggle with too much down low. I was thinking of trying a .96ar first.

6. I'll have scavenge pumps that will pump too and from a 1'' spacer on the oil pain and I'll run a oil cooler. Should be adequate

4.

 

I can get this turbo for $350, which seems like a pretty good deal. I can upgrade later if need be... any feedback in trying this first???

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The units on sale are the .96 turbine housing.

 

Don't let your excitement get the best of you. I did that and ended up with turbos that are too big.
My car is a 3.8 Liter v6. I certainly wouldn't want a .96 turbo especially mounted in the rear until i was built to rev to the moon, possibly beyond and with force with this type of displacement. Good thing you have nitrous.If it will help that turbine size
And yes, i have experimented rear mount with a .48 baby turbo but without nitrous. Couldn't hear it whine until i decided to move it to mid-mount.
I myself definitely wouldn't think about using a .63 to4e for rear mount.That may be best left to the bigger engines.

BUT your car is different so results may vary. My car is a 2v mustang.

Whatever route you choose to go let us know how things are going and post pics of the build. Always interesting to see how things look whether they work or not. Let me see if i can find a pic when i had a rear mount .48.

 

Mine went up and made a "U" over the axle and worked some 90s and a 45 degree through the front fender well. Even custom fabbed so the turbine pointed out the back in case it fired some cool flames.
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