Xcessive

We're deciding on wether or not to produce these twin turbo kits. Just wanted you guys to give me the extra push to do them. Here is a pic of one our builder has made before. This here is equal length runners in case you can't tell by the pic



The acual manifold will be made with T3 flanges so any set of turbos from GT28R's to GT35R's can be used.

Anyways, let me know guys

aarroneous

iTrader: (5)

Hi, it's hard to make a decision without getting a closer look at the workmanship of the exhaust manifold. It's very cool that you guys were able to get equal length runners in that area - just have a few questions. What's the diameter of the runners, and how does the hot side merge into the downpipe? What diameter for the downpipe? Will your kit bolt up to any aftermarket mid section (assuming that they have the proper fitment to begin with). Is it set up for (an) external wastegate(s)?

Oh, maybe this is a dumb question, but I thought that the GT28R uses a T25 flange. Are they actually the same size?

Oh, what material will be used? Are there any support braces (probably unnecessary depending on material, but better safe than sorry).

Sorry about all the questions, but I hope you just realize that I'm in fact *very* interested in such a kit.

Last question - will you offer this kit without the turbos?

TT_Rex_7

Twin GT28RS turbos would be fine, but anything larger starts to be to large. However, that's all in the eye of the beholder. A PP/BP engine will do fine with those large of turbos. Any other type of port (mild/large streetport) i'd stick with GT28RS, or smaller turbos.

-Alex

TT_Rex_7

The workmanship/welds are great! John (LT1-7) has great fabrication skills! You should search his name, and look at the fabrication he has done to his V8 rx7. I'll post some pics of the manifold later.

The ID of the runners, in the manifold pictured, are 2".

The GT28R comes with a T25 flange, however Precision might offer it with a T3. You'd have to verify that with Precision/Xcessive. The GT28RS, and up, are for sure offered with a T3 flange.

That (mine) manifold is made from schedule 40 304 stainless. The T3 flange, and engine flange, are made from 1/2" 304 stainless. With the material used, bracing isn't really needed. I highly doubt it'd crack.

I have my manifold, along with 2 GT3071R turbos for sale! PM me and i'll send you some pics and a price!

-Alex

TT_Rex_7

WOW! I feel like a real jackass!! I must of been in another world when I first measured each runner. I went down to my shop tonight, and re measured each runner. They are in fact equal length, within ~1/4". However, keep in mind, that 1/4" could be measurement error. It's a PITA to measure these runners since the whole manifold is all welded together. I'd say they are within ~1/8" or less of being equal length.

I'll be notifying the moderator of this section, and hopefully he can delete the comments about the manifold being unequal. I don't want to spread false information!

-Alex

Edit: BTW, pics will be posted later tonight.

7knight

what kind of number could be expected with a large street ported motor running GT3071's? also assuming all other necessay mods are done. i.e.- front mount, fuel system and so on?

TT_Rex_7

Not sure if you just neglected to read my post or what, but I wouldn't run a set of GT3071R's on a street ported motor. Your looking at some serious lag, and a real snail on the street. If your looking to put 2 GT3071R turbos on a street ported engine, setup for drag only, then they're fine. Other wise, either go PP/BP, or run something like a set of GT28RS turbos. Either way, to answer your question, each turbo is capable of producing ~450-500hp on a piston engine.

As promised, here's some pictures of the manifold, and one of my feretts!







-Alex

Jason

iTrader: (5)

We tested a twin GT28RS kit and found that its not worth the extra cost. They didnt out perform a single turbo and didnt spool any quicker. Larger turbos are going to be real laggy. They did look good and a unique setup.

Jason

RETed

Can I ask why is it do important to have equal length runners on this parallel twins system?


-Ted

dubulup

^I was wondering the same thing?

Seems optimum length would be the best bet.

--MAstermind--

i was wondering the same on a twin turbo car how important is it to get equal lenth runners? i mean they arent sequential right? so they are both spooling at the same time? would it matter? or would it help flow equal volume of air ???

looks nice..(wow taht turbo is MADD close to the enginebay....lol fd = crazy
seems like astheitcs to me i suppose?

Zero R

iTrader: (1)

I wouldn't say it is as important, but you would have a pressure differential from front to rear, which leads to other issues. If they are close like what it seems to look like it would be negligible. The twins set up can be good thing, but you need to do your homework. Just slapping two turbo's on will not be ideal and you will end up with average results as in RX7store's experience.

BLUE TII

iTrader: (9)

Why would you want a twin system with individual uncollected exhaust runners?

It would seem to me if the two runners were equal length merged like an "X pipe" it would double the pulsations in each runner smoothing out the sharp rotary pulses.

This would seem to be especially advantageous when using the GTQ exhaust wheels biased toward "reaction" effect as opposed to the rotaries strong performance bias toward "impact" effect on the turbine.

Jason

iTrader: (5)

Since Im sure you have done this setup many time whats your experience? Any dyno graphs or data?

Jason

TT_Rex_7

I'm not sure if that statement was sincere or not, but I to would be interested in knowing this.

-Alex

Jason

iTrader: (5)

It was sincere

Jason

TT_Rex_7

Well, i've spoke with Precision and Innovative, and they both said to go with a large single over a twin setup.

For starters, it seems to be a slight "secret" properly sizing a turbo for a rotary. As i'm sure you already know, most common knowledge about sizing a turbo to an engine is for piston engines. Adding a second turbo just makes things more complicated with sizing the correct turbos.

They stated that there are benefits to twin setups, but with my application (rotary engine), it *could* become a trial and error process. I wasn't about to spend $$$$ on various diffrent setups, when I could just go with a single. In other words, I went with a GT40R. I'm curious to find out if A-spec has done any trial and error.

They recommended to stick with a single, and only use a twin setup for higher power output. Of course you can get just about all the power you want with a LARGE single, however, anything larger than a GT42R is a real bitch to fit in the engine bay. The main problem with trying to fit a larger turbo is the width. There just isn't alot of room between the engine and engine compartment. (Partially because the intake manifold eats up ~2" of that space) However, by using 2 smaller turbos, that will flow more combined than a GT42R, will fit by placing one above the other, just like the pictured manifold. My intake manifold (custom) eats up ~4-4 1/2" of the space, so both the GT42R, and the twin setup was out of the question. So was a short runner exhaust manifold.

-Alex

Zero R

iTrader: (1)

I've done trial and error over and over on paper as well as mocked one up. When you add up the added cost and complexity for the amount of efficiency you gain it really serves no purpose on a street car other than oooohss and Ahhhhhs. People are seeing 1bar by 3800rpms or better on GT42R's. That's with 1.15 large frame turbine housings. They are making over 600hp with them at around 1.7 bar on well built two rotors. Everything I've come up with says if your going to go twin go bigger than 28's you need at least a GT30 compressor and the appropriate porting and good plumbing. Run at least a T3 flange and build it for higher boost applications. If I ever get the time or someone wants to drop off a car and some money for a complete build I will put a nice setup together. But for me from what I've come up with a well sized single does the job just fine for most needs.

SpoolinRX

iTrader: (6)

Sorry to hijack but, I wanted the GT40R but I hear it’s on "indefinite backorder". What is out there that is gonna replace it?

TT_Rex_7

I got my GT40R from http://store.yahoo.com/cheapturbo/index.html

A few weeks ago they had 2 in stock, and I took one of them. If your still looking for one, give them a call, they might still have the last one still in stock. FWIW, I picked it up for $2,100.00 with next day air, so their price seems to be on par with everyone elses.

-Alex

SpoolinRX

iTrader: (6)

I can find it on the website, where is it? All i can find is the GT40 and thats not a BB.

TT_Rex_7

For whatever reason, they don't have it listed on their site. That's why I said to call!

-Alex

TT_Rex_7

I've noticed for quite some time that you've had a twin turbo kit listed on your website. If I recall, the release date was supposed to be April. Whatever happened to that, and what turbos were you planning on using?

-Alex