If someone were to want some sort of modified twins capable of 500HP how would you go about it. Obviously the BNR's will get you to 425 or better, but what other ways have the members considered???

 

The stock manifold is way too restrictive for those levels. Plus good luck finding turbos large enough to bolt onto it. The only way I now of is too go the Howard Coleman route.

 

Turbo's large enough to make enough CFM for that particular power, and a whole lot of fabrication with the manifold & piping.

And of course a healthy ported engine & all the supporting systems.

If you are Johny custom & have the shop to make it happen then go for it. Otherwise, I'd go with a quality single kit, make good numbers & be done with it.

 

Howard Coleman had twin GT35's. I think he made over 500whp. His setup was for sale on here a while ago and went really cheap (well cheaper than I expected). That looked like it'd actually be pretty easy to duplicate (they weren't sequential or anything).

 

I'll see if I can track down Howard to ask him what his opinion is. That said

i understand the need for porting and I can see how the stock manifold is restrictive. But, isn't there some room for manifold porting or clean up.

 

They were twin to4.

If I had the money and the tools and time I would recreate the sequential twin system with a custom manifold like it has been done on Supras... Or I would go compound turbo with a small quick spooling one and a large top end one... Or super and turbo twincharge like the recent thread in here about it...

 

On HC's setup I believe they were twin T3/T04E 50 trims off the top of my head, internally wastegated. I'd have to go back and look at his plumbing again. It wouldn't be THAT bad. Use compressor with compact housings and small inlets, and take advantage of the internal wastegate to cut down on plumbing. Remember that there would be only two exhaust manifold runners.

 

http://www.atpturbo.com/mm5/merchant...egory_Code=GRT

If you've got the money you can go with twin GT3071R (or even GTX if you are baller) using the 2.75" compressor inlet and vband turbine housing inlet. That will help with fitment constraints. There are also older style T3/T04E variants to use. You can go with a Master Power or other less prestigious brand to cut costs further.

 

ARGHX, any thoughts on if this would work for 500+ twins with sequential functionality?? I was looking at their ultimate wastegate as well. I think that and an 18psi actuator would be more than adequate provided it's even possible to do this the way I'd want it done.
For those who don't know I would want the twins to behave like the stock twins to maintain the powerband minus the 3K stutter.

 

If you wanted sequential, you'd basically have to build a manifold that would replicate the OEM one in functionality. You could even use all the OEM controls for it as long as its replicated the same. Not an easy feat, but I don't see why it couldn't be doable. However, for less trouble you could just run compound turbo's which would have the same goal but be simpler. Possibly a GT30 with a custom turbine and T4 housing and then a GT42 (maybe something a little smaller)



thewird

 

Wird,
The thing with compounds turbos and the FD chassis is that things are tight in there to begin with. I personally have only see it done successfully once. and that was on a 20B with a highly modified hood. I'm not saying it can't be done just that it's not my cup of tea ; unless it's something crazy like a 20B then I'd try it. As for the manifold, I'm thinking about trying to use the factory manifold and simply upgrading the turbos to increase flow. Maybe some porting of the manifold as well to maximize the design as much as possible.

 

I don't think it would be possible on the stock manifold. At least not without some clever re-engineering of the manifold.

thewird

 

A high-flow sequential manifold would be the sh*t, with a set of GT25's or GT28's on it. Even the BNR's or the old M2 BB's never really got the full potential out. Unless you go non-sequential and/or jack the boost over 15 lbs, you ain't makin' 425 at the wheels on a normal setup. But you could probably with a better-designed manifold.

I suspect you'd have to 3D model and cast something out of some kind of crazy material. The constraints are too tight for welding mandrel-bent tubes together I think.

 

[QUOTE=ptrhahn;10449797]A high-flow sequential manifold would be the sh*t, with a set of GT25's or GT28's on it. Even the BNR's or the old M2 BB's never really got the full potential out. Unless you go non-sequential and/or jack the boost over 15 lbs, you ain't makin' 425 at the wheels on a normal setup. But you could probably with a better-designed manifold.

I think that the manifold could be modified or at worse only slightly re-designed to get more HP potential from it. That said cast iron would have to go. It's simply too heavy and too difficult for the average person to make. Stainless would be acceptable, and I'm wondering if ultra short runners could work. Spool-up wouldn't be a problem and just giving it a passing thought I only see making the mounting flange being an issue, but that can be CNC'ed . The internal wastegate could be based on the ATP ultimate wastegate.

 

^^^

Build it, and they will come. I love me some sequential twins, so I'd be in on something that worked.

 

staring at solidworks as we type. But I'm pretty sure that I'll just have to use me far from superior fabrication skills to mock something up .

 

what's your thinking about this. That manifold looks serious BTW

 

The exhaust manifold (the part bolted to the engine) isn't really the problem, although some work there can help. After extensive testing, I have concluded, as have others, that the real restrictions are the turbine housings with their small A/R. This is followed by the proximity of the turbine outlets to each other; there would likely be a benefit to spreading them apart and improving the turbine exit.

I also spent a lot of time looking at the twins package and realized that some of the constraint is due to making them JDM compatible. In the USDM package, it appears to be possible to locate the rear turbo further back which really could help layout scenario.

 

There are too many cost and reliability constraints to do this with sequential twins.

 

Speed, your right the RHD steering has always been a restriction on OEM turbo cars. Also the manifold isn't really a restriction so much as poorly designed. for expandability. I agree 100% that the turbines are the a major restriction, and had they been better thought out, I see no reason why the FD couldn't have been a 500 HP Mazda Supercar from the factory ( gentleman's agreement not withstanding). Sequential turbos were and still are a great idea if the package is properly executed. A setback on the twins rearward would also allow for larger turbines and this more power. However with size comes lag, and that will be hard to get around. well, maybe not hard just time consuming.

 

Mazda doesn't think the way most people on internet forums think. Above all they went usable torque by 2000. There is an SAE paper describing the design process used to develop the sequential twin turbo systems (paper focuses on the 20B). PM me if you are interested in this.

The turbo manifolds and turbine housings for the twins were supposed to be as small/restrictive as possible without causing excess backpressure. That significantly helped transient response. The 13B and 20B were designed to have the torque curve of 6 and 8 cylinder naturally aspirated engines.

 

Attached are the torque curves for the series 4 turbo (variable A/R hotside system), series 5 turbo (divided twin scroll manifold), and series 6 twin turbo, and 20B twin turbo engines.

 

Maybe 500 rwhp isn't reasonable... but if you were able to have the same or better spool-up and torque of a sequential '99's or really small BB single (4X6B), with the top-end of a bit larger single (35R or 500R) or non-sequential BNR's, that, to me, would be worth the hassle.

 

BNR is claiming 426 with their stage 3's so I think 500- 600 wouldn't be completely unreasonable with the proper upgraded turbo's.

 

Well, that's non-sequential, and probably not at 15 psi. I've never seen a sequential dyno over 400 hp, at least not at anything that is a sustainable boost level.

The top sequential dynos are about 385.