Have you thought about switching the A/R on your turbine side? I don't know what it is now but assume its a .96.

 

You are correct, .96 standard Gen 1 VS racing 78/75 with the billet 11 blade wheel. I wasn't aware of a different AR housing. Maybe I can reach out to Viren and see what he offers are you thinking like a .81 AR?

 

It's worth a shot, anything smaller will choke your top end.

 

I also have a 76/65 with a .84AR that I used to run. Do you think thats worth a shot? Its just as standard cast wheel CX racing turbo.

 

Ive got a billet 76/65 sitting on the shelf as well. It spooled wicked quick, but ran out of steam at 6k. I mean if you've got it you could try it, but I think you'll be giving up quite a bit of power above 6k. It'll essentially make it a big cube NA motor.

 

Gotcha, hmmm. I see VS offers a billet 70/70 which would provide enough air 9(rated for 1100hp flywheel) but has a larger exhaust wheel and comes in .81 and .96 AR. Thats pretty close to the S366 specs but has my 3" DP vband and its a small frame turbo. I don't really spin higher than 6000-6500. Car spends 98% of its time below 6k and 90% of that is below 4500 for street driving. BB power and something that will rev to 6-6500 is my ticket. I also don't want to push more than 15-16psi with ungapped rings and I'm maxing out my 72lb injectors.

 

maybe check out the smaller A/R on the current turbo. Covers are cheap.

 

They have a .68 T4 for the 78/75. I'm not aware of any between that and the .96.

 

https://jansam.ca/performance-world-...im-black-oxide

 

Learn something new every day! Wonder if you could get just the housing, seems pricey!

 

That's what I'm wondering. If someone sells the entire turbo, surely we should be able to find the turbine housing from somebody.

 

Well If I really wanted to try this and you guys think it could be a worth while mod to help a bit with the spool I found the .81AR 78/75 cast on ebay for $280. At that price I could see if the housing swaps or just say screw it and run the whole turbo and be done with it. At my boost level I don't see much of a benefit of the billet wheel anyways.

Will the .81 have a noticeable change over the .96 AR?

 

The only thing that has me concerned is you said 500-1000 rpms earlier spool. I dont think a .81 from a .96 will get you that. I would almost say just go back to the 7665 and see what you think since you already have it.

 

I'll see what I can dig up on in old logs. I remember and found some stuff online that showed boost always starting at 3k ish and full boost by 4000-4500 and that was with the 76/65 .81AR. These down show me going WOT from a dig but me rolling into it. This was with the old Fitech ultimate LS. If I'm going to do a swap out I def want it to be worth while... start building boost 2000-2500 would be great which is 500-1,000 rpms earlier than I feel it comes in now. I would love to be All in by or before 4k.

 

Why is your TPS so low?

 

These are old logs from Fitech and I was running 275 summer tires which didn't give me much grip at all so I had to roll into the throttle to avoid spinning bad. When I get home I'm gona look and see if I can find a better log. I don't think I have any logs with the new holley system.

EDIT: unless your talking about the 2nd image where boost started at 2k and TPS was low that was a 4th gear pull with a locked converter.

 

The first 2nd and 4th pics all show low TPS %.

 

I may be missing something here , bear with me here . First is 100 % street car - traction limited. Your 2nd log (converter locked) shows starting to boost ~ 2100 and 24% tps , if that was 100% it would be even sooner . Converter flashes to 3000 ish , which is approximately where boost starts in the other logs - not a coincidence, not going to build much if any boost below stall rpm and even less likely to if not WOT . If you're rolling into it because of traction then I see no point in building boost earlier. Not trying to be an *** here , I don't understand the goal I guess. If you have a log with 100% tps that can somewhat show the spool characteristics that may help , if you can't because of traction then you don't need quicker spool and you can save some time and money . Does that make sense?

 

Those I believe are cruising in 4th with the converter locked. Think I did a 3rd gear pull and at the top shifted to 4th and coasted, then cruised in 4th till I got to an off ramp and I could make a U turn and repeat.

 

From a Dig on a street road the car spins before boost even with the DR's so traction above 60% is a problem even before boost hits the equation.

At 2100 & 24% TPS I'm cruising at 70ish+mph so the TB is barely open and load on the engine is high (converter locked so its like a manual) so its easy to build boost through a 1/4 of the blade position. I can build "boost" according to the MAP sensor at 1400 or 1800 if I load the engine low say 40mph in 4th and the converter is locked and just give it alittle gas.

I dont think there is an decent NA car that you can be cruising and WOT and not break the tires loose from a 30-40mph roll especially if the trans downshifts. BUT I agree with the converter and not allowing it to build boost as easy as I think it should. I hear that just because you have a 3800 stall converter doesn't mean you don't build boost till then... you can start seeing positive pressure before the stall. Just because the engine is "slipping" and has reduced load it can still build boost if the turbo is sized right.

Turbos are not like superchargers or NOS, they have lots of variables. I can be in boost at 3500 in 50% throttle but not in boost at the same RPM at 30% throttle. I think what I'm looking for is a more responsive turbo like the feeling of a stock OEM turbo car where boost is very low in the RPM which gives you more tq/hp under the curve to help you scoot around where 90% of people stay during driving. I guess if I can start building boost with the 78/75 at 50% throttle at 3k and be all in by 4000-4500k i would rather start building boost at 2500 and be all in by 3500k which means boost rolls in sooner and gives me more usable power in the mid range for my street driving. I don't and NEVER get to spin to 6500+ on the street as you see in the logs I'm about to post that I usually cut out around 5500-6k as going that fast on public roads is like 120mph and not really the best idea. The billet 75/78 allows me to spin to 6500 no problem and would probably allow me to spin to 7k and still make power. My goal would be to max out at 6500 on this gen3 motor so I'm looking for a turbo small enough that will build boost starting in the 2000-2500 range and be all in by 3500ish, then carry that out to 6000/6500 and be out of steam. I really the stall will affect that and the added torque from boost will make it stall higher.

I was able to get in touch with Viren and he doesn't sell the .81AR for the 78/75 and I brought up the 70/70 billet he said it would spool about 500rpms sooner than the 78/75 and be all done by 6500 and would be done around 650-700hp on the 5.3. That sounds kinda perfect honestly and its a small frame turbo with the 3" DP I need so it should drop right in hopefully.