twin turbos are exactly the same size. the turbos in the supra are spooled sequentially where all the exhaust goes through the first turbo and spools it quickly then the exhaust is routed through both turbos for high end boost.

 

aftermarket twins spool in parallel. from the way you phrased your questions i get the feeling that you think they spool one after the other, which is infact not true.

in terms of the part 2 question...first off realize a t78 is not much bigger than a t66, slightly better top end, but sacrafice a little spool... these numbers are taken off of Steve V.'s www.moreboost.org, but this will give you an idea of how close they actually are.

Turbonetics T66: Compressor Inducer 65.5, Compressor Exducer 91.0, Turbine Exducer 64.6, Turbine Major 74.2, .70 and .81 a/r's

Greddy T78: Compressor Inducer 66.0, Compressor Exducer 90.0, Turbine Exducer 65.0, Turbine Major 74.0

both of these turbos are good for about 700rwhp properly setup

either way...even if you could get it done sequentially...neither one of these turbos are going to give you "good low end"

also, where did you see dual t67's? was it on a supra? keith ta has dual t66's but you have to imagine that thing spools in an hour. he has a low 18psi 740rwhp graph on www.T04R.com

 

This is a good question. Seems like a great idea, but I've heard that it's not quite feasable for some reason.

 

reason its not feasable (to my knowledge) is that it would be EXTREMELY expensive to engineer a larger turbo kit that utilizes sequential plumbing, think about how hard it would be to route everything to a t66, then have some solenoid switch over and plumb all of the air over to a second turbo.

 

Would it be possible to set them up in parallel, but use a VERY small turbo coupled with a medium sized turbo. This way the small one would spool quickly even though the gases are trying to spool both turbos, then the immediate power from the small turbo would be used to spool the larger one? Just a thought, although I don't have very much knowledge of turbos and if it was that easy I'm sure someone would have done it by now. Just food for thought.

 

Why not just use a twin scroll design so that you can change the A/R?

...or a VATN turbo?

You guys need to read Maximum Boost.

 

the problem in using the normal parallel twin setup with a very small turbo as to "jump start" the bigger turbo is that, even though thats a good idea, you must remember that it is only being spooled by 3 cylinders and not 6, so even that small turbo wouldnt spool ultra quick. a GT2835 (the second smallest garrett/hks gt turbo i believe) still takes a long time for only 1.5 liters to spool, thats civic displacement (1.6) also once you jumpstart this second turbo, you must remember it, too, is still only running off the other 3 cylinders. and once both turbos are in parallel, if the second one is big enough to warrant this project it will probably have a significantly higher top end than the "bottom end" turbo, and if it is pushing this much air through the engine, it may prove to be too much for the smaller turbo and take it out of its efficency range. of course this is just things off the top of my head, you may be correct and it may work very well im just playing devils advocate and giving reasons why it might not work.

btw quick, i have the book, but im only in the first chapter

 

Isn't it a great book? I learned a shitload from that baby -- that and talking with gixxer_drew.

Sequential twins are good stuff. the main downside is complexity. Parallel twins are fine for V-engined cars and super-lightweight turbo wheels, etc. Expensive to get that type of hardware (lw) though.

 

haha, drew definately knows his stuff. and yeah so far i love the book its like car guy porn. i heard he wrote another one called "supercharged" ill pick that one up after i finish this one.

definately hear ya on the sequential. and i have exactly the same opinion, if i ever get the cash (after i finish the supra) to build a C5 it will run on twins. but for the supra, im starting to research nice 600-680rwhp turbos that get full boost and over 300rwhp by 4k. 66mm seems to be a good size

it would be really cool if someone ever did come up with a big sequential setup, just i imagine it would be EXTREMELY expensive if not to just recoup the R/D costs.

regards,
Mark

 

Well my friend said it was a T67 cuz we went to Long Beach Hot import nights and saw a few supras and M3's. I , loving both these cars as much as I do, undoubtfully nutted in my pants 50 times. Yes five..... zero.... times. He said he saw a Supra with twin67... I was like whoa really?! and he showed me on a cam corder. It was hard to see what was really in it cuz he was shaking alot. Maybe masterbating himself...? But yeah, I doubt it was 67's. Most likely it was Keith ta's supra. By the way is there anyone who would like to chat online about Supra?! I love the car so much I wish I had someone to talk to about it? I kind of also lack knowledge of cars so Unless you don't want to be pestered with n00b questions... heheh. Just private message me your aim... and I will holla back! Thanks for info. Maybe someday someone (hopefully myself) is going to get sequential twins with a small turbo and the Mr Monster Massive T88h. (Imagine this turbo reaching max boost faster then you can say "I love supras I love supras I love supras I love supras I love supras I love supras I love supras I love supras I love supras I love supras I love supras " and so on... AHhaah jp.

 

hahah the t88h is probably going to out flow any small turbo, also like i said before...3 cylinders spooling a t88? oh...my lord...youd get boost at about 6700rpm... haha

and if you have any questions you can talk to me if you want "AXAdiablo" <--aim

 

Quick, whats a VATN? Is that like a variable aspect ratio turbo? Why hasn't anyone tried experimenting with those? Too expensive?

 

borg worner (KKK turbos) is working on variable a/r's.

 

Quick, whats a VATN? Is that like a variable aspect ratio turbo? Why hasn't anyone tried experimenting with those? Too expensive?

The primary problem with these are reliability and capability. The ones I remember (mentioned in maximum boost) are only good to ~15psi, 20max. They are also self contained (no oil or water lines needed). This sounds cool, but I haven't heard the best stories of longevity for them. The compressor map for them looked better for a larger engine running twins rather than the small 3L supra engine. These turbos could flow a pretty good amount of air but only at these low boost levels. Anything over a pressure ratio of like 2-2.5 and it becomes very inefficient. I suppose with the use of two of these turbos on an engine with higher compression these may work ok.

For those of you who are now asking where I saw a compressor map...I have one somewhere that they faxed to me like 5 years ago. I will try to find it, but no promisses.


Daniel

 

A while back there was a twin VATN kit for the 3S-GTE. If you go to the MR2 boards you can look up Pouya who lives in so cali. He has the twin VATN kit for his MR2.
Problem with the VATN was that it couldn't hanlde higher boost levels. Even with twin VATN turbos you wouldn't get any real benefit compared to a single 60 trim turbo.
As far as an aftermarket sequential set up, RPS was making one, but I haven't heard from Rob Smith about it. See if you guys can find out anything from him.

Chris

 

No real benefit? Wouldn't it outspool a fixed-pitched setup?

 

Last time I heard, Rob Smith was still working on the sequential system. Be prepared: around 10K$ price tag...

-Olivier

 

Quick fix: big turbo + nitrous + hob switch

Long,

 

2 of the biggest VATN turbos are only good for about 500HP and no more then 20psi of boost, why do you think this concept was never used on a supra

Why not just use a twin scroll design so that you can change the A/R?

...or a VATN turbo?

You guys need to read Maximum Boost.

 

2 part question.

Part I.
Exactly how do Twins spool?

Part II.
If they spool how I think they do... Is it possible to... combine a, lets say T66 with a T78? So that you can good low end and later High top end?

Just curious if its possible and if other people have thought or done this? I've seen dual T67's this is what gave me that idea. Noob(me) yes I know. SOrry

At the end of the April 2003 Turbo magazine (big tech issue) they have an article on multiple and staged turbocharger systems/strategies. Heres what it says:

"Multiple sequential turbos? Harness all the exhaust energy to actuate a single turbo for excellent low end response, then open some valves and bring a second turbo online when the engine's air-flow requirements being to exceed the capacity of the first turbo. --------
Staged Turbos? This method is great for super-high boost applications (50Psi) where the required pressure ratio for a single compressor would be too high for reasonable thermal efficiency. With compound turbocharging, you step up the air pressure a reasonable amount (say, pressure ratio of 1.5 to 2.0) with teh stage 1 turbocharger, then intercool it. Then feed the Stage 1 pressurized charge air into a second Stage 2 turbo to pump up the boost to extreme levels with another reasonable pressure ratio (followed by a second stage of intercooling."

Sound exactly like what you're looking for in the top one. Almost sounds like the stock sequential system, but with different sized turbos (like you wanted). I will look further into this and see what I can find. Hope this helps!

Rob~

Didn't read through all the posts before I posted, but this has to do with the Borg-Warner systems they are developing.

 

Rob - The first thing you described is the stock twin setup.

If you have one larger turbo come on 2nd then you're going to have a big dip when the transition occurs IMO.

 

Rob - The first thing you described is the stock twin setup.

If you have one larger turbo come on 2nd then you're going to have a big dip when the transition occurs IMO.

Thats exactly what I thought, but it seemed to be exactly what the guy who made this post was looking for so I thought I'd post it.

Rob~

 

Thats exactly what I thought, but it seemed to be exactly what the guy who made this post was looking for so I thought I'd post it.

No sweat. Based on some of the dynos I've seen if you pick the correct turbo you can make killer power (with excellent spool) even with a fixed-vane single. :bigthumb:

-Chris

 

i know the biggest i've seen in a mag. was a Twin T78 ....
JUN Talk about monster

 

No sweat. Based on some of the dynos I've seen if you pick the correct turbo you can make killer power (with excellent spool) even with a fixed-vane single. :bigthumb:

-Chris

occationally a properly setup small-mid single (up to maybe a T64, can spool near identically to a TTC BPU, and just majorly out pace it on the high end. i would guess that with some nice headwork, a T66/T78 could spool about the same, 300+rwhp and full boost by 4000rpm...now that would be a street/track (road course) monster.