1994 FD gone in for rebuild and street port after been parked up for nearly 5 years. Got a GT4088 on it with less than 1K miles but before engine broke it was not getting full spool until 4500RPM.

I know that the street port will now improve this but doubt it will bring it to anything near the 3200 - 3500 RPM I'm aiming at. Don't think I'll have enough $$$$ to splash on a GT35R as well. Any options or recommendations, perhaps alter the housing on the GT40 I got?

 

The GT4088 is the wrong turbo to run on a stock or street port if you intend for it to be responsive.

Downsizing the turbine housing will help, but then, as is a common issue with small turbine housings, you will run into a turbine too restrictive than for the compressor.

Best bet is to sell the 4088 and pick a more appropriate turbo.

Which brings us to: how much power, what is the use of the car, etc.?

 

Car is meant for street use over weekend with occasional every other day use and maybe for track events every now and then.

I realized pretty much that the turbo wasn't what I need after the single turbo conversion but I picked it up along with the whole kit cheap from someone who abandoned their project.

I told the guy who's doing my porting and rebuild that I'd be happy with 400whp and he said he'll send me a list of recommended turbos but since he's not touched my car yet he hasn't done so.

Just out interest how does this Holset compare to the GT40 that I've got and GT35R?

 

The HX35 is a popular turbo choice for stock and street ported cars. Best bet is to head over to the Single Turbo forum and take a look at some of the Holeset threads. I have not used any Holesets myself and therefore cannot give a recommendation past reading the spec sheets.

What I can say is that I've had very good success with the 35R in the 350 - 380 HP range with the smaller .90 turbine housing. Very responsive from 2500 RPM up.

 

That 4088 seems crazy big, but probably hits really hard. You may be able to get it to spool lower with big intake and huge exhaust, but with the stockish motor, it may not help much.

 

Ok, here's an update. My engine rebuilder recommended the following, Borg Warner Air Werks S300SX3-60 / S360 for a street port or Borg Warner Air Werks S300SX3-66 / S360 for half bridge/full bridge port.

 

I have a friend who just went from a Garret GT35 to a BW S300 .66 and they seem really happy with the change, they have a rather responsive spool time given the right mods. And relatively inexpensive for what you get.

 

hey what hotside are you using ? i have a gt35r but i cant decide what ar size i want for the hotside i have the .82 t3 on it right now but want to get a t4. i just dont know wht to gho with th t4 .82 or should i go with the 1.06 ar? could you give me some insight on what way to go

 

I'd suggest the 1.06 T3 on the 35R for most street applications. Very fast response, good to about 400HP or just under before it starts to really become restrictive.

Rotarys need to breathe. Much larger turbines are needed than a piston engine. That .82 T3 housing will make boost off of idle, but run out of poop around 5000 RPM. I've tuned a car with that combination before and it was a blast around town but it required about 18 PSI to make 380RWHP and boost would always taper at around 5K RPM. I'm sure pre-turbine backpressure and EGTs were ridiculous.

 

You think it would be a huge difference between the t3 1.06 and the t4 1.06? For spool times and do you think the turbo would tap out if it were a t4 .82 or does it not make much difference between the two?

 

It's an enormous difference between 1.06 T3 and 1.06 T4. The T4 turbine wheel is much larger, as is the housing. Just the A/R ratio is the same.

A 1.06 T4 is for a large port, such as a very aggressive street port or bridge port.

T4 .90 is the way I would go. .82 is a little small and will start to taper off. .90 is still going to be very responsive and the cars I have tuned with that combination (60-1 turbo, very similar to 35R) have worked out very well.

 

Turbine wheels do not EVER change on a GT3582R( aka GT35R). I have never seen anyone use a Holset in person. I have tuned 600+ Rx7s.

 

I'v3 decided to go with the BW S360 with a .91 AR as I'm sticking to street port for now(Borg Warner Air Werks S300SX3-60 / S360 Turbo (Type A) [177272] - $724.25 : Himni Racing, Turbocharger, Turbo, Garrett, Turbo Kit, GReddy, Mazda RX-7, HKS, Apexi, TiAL, TurboXS, TurboSmart, Flange, Turbonetics, Exhaust, Intercooler, ACT, Intake).

Hope to have this here over the next 2 weeks as engine now getting ready to be stripped and prepped.

 

Im not quite in the same boat as you, but I'm going from stock twins to single turbo, its all torn down ready to get the new setup though. Right now I'm just waiting to decide which turbo to choose. Ive been swayed towards the s362 but the fact that its only oil cooled and journal bearing worries me a bit. Anybody thats already chimed in, if you went s362 would you have regrets on not going with say a s366/35r and would you go divided on undivided? looking at 15psi for a streetable 350-400hp.

 

I ended up ordering S362 only because every seller that seemed to list the S360 mess about and waste time. So ordered from a local seller instead of international S362 which I know in stock and will be with me here by next week.

 

This is what I got, so long it gets me 400+ whp and full spool under 4K RPM I'll be happy with it.