Twin GT35R or GT42R

[Lextreme II]

What do you guys think? Twin GT35R are rated at about 1,300 hp and GT42R are rated at around 1,200 hp. For the SC400 there is enough room between the engine and the radiator fans. Which setup would you want if your goal is 1,000 hp? Here is a good turbo specs of the two turbos.

Price
GT35R: $1,395.00 Each Total: $2,790.00
GT42R: $2,329.00

Additional Cost
Additional Wastegate for twin.

 

[stevechumo]

I'd go for a twin GT35Rs. While the GT35Rs can do the job, why should I risk for the turbo lag that bigger GT42R will surely give? I like to feel the boost kicking in due to the turbo, but 1/2 second of turbo lag wouldn't make me happy. How about a triple turbo? 3 GT30R or GT28Rs will give tremendous power at low-end and monsterous power at high-end. Who'll know the name: "David with a triple turbo design & his new innovation" will become popular. The concept is the same so if the triple turbo is carefully thought of, I'm positive it'd doable.

 

[Lextreme II]

I don't have the calculation, but I am not sure if the twin GT35R would spool faster then a single GT42R. Remember you are running one GT35R with 2.0 liters or in my case would be 2.35 liters or you can run one GT42R with 4.7 liters. I wonder what is the spool time of a WRX (2.0 engine) would do on a GT35R.

Here is a GT42 dyno on a 3.0 liter Supra (24 psi). The graph below represented a 3.0 liter. I am not sure how would a 4.7 liter would look like, but I am sure it will alot sooner then 3.0.


Here is something very similar to the 1uzfe dyno. This is a GT35R in a MR2 (2.0 liter at 24 psi)


The last picture is the GT3071 in a STi (2.5 liter)

 

[turboandrew]

I would agree the twins won't always spool sooner. In theory, they do. In practice, I rarely see that happen. But even so, either choice seems like a win

 

[Anaema]

what about quads

 

[WDoherty]

well i know people have complained about the lag on 4 cylinders as daily drivers with the gt35r so even with two of those you are going to have a good amount of lag, not sure with a singe gt42, but maybe similiar. Anyhow, if you are going for that much power, expect a good amount of lag and power in the top end probably after 4k you'll get full spool.

 

[WDoherty]

The GT3071 on the sti spooled fairly well, maybe you'd be better off with two of those. Basically look at what the 4 cylinder cars are happy with and go with two of those, the wrx, neon turbo, honda turbo set-up should give a good look and i think alot of those point to the GT3071.

 

[Lextreme II]

I think there is a misconception that twin will spool faster. Its all depends on the size. Two T88 would not spool faster then a single T88. I think we have put this in mind when u do twin turbo. Just make sure you divid your engine size into two. It will get half of the exhaust gas and half of the heat. So for a twin turbo 4.0 its literally means two 2.0 engines. I am not leading toward either one, but just to open up some points.

Unless we can do some type of sequential the twin would be awesome.

 

[Anaema]

I think there is a misconception that twin will spool faster. Its all depends on the size. Two T88 would not spool faster then a single T88. I think we have put this in mind when u do twin turbo. Just make sure you divid your engine size into two. It will get half of the exhaust gas and half of the heat. So for a twin turbo 4.0 its literally means two 2.0 engines. I am not leading toward either one, but just to open up some points.

there are several different ways to setup a twin turbo system. for the 1UZFE you could do a seperate manifold and turbo for each bank of cylinders, or you could do a parrallel system that combines the two manifolds and then routes the turbos together via a small downpipe. the latter is used in diesel engines.

 

[Lextreme II]

Here is a nice example of GT30R on a 2.0 liter Honda at 26 psi

 

[WDoherty]

that looks good, go with two gt30r's. i wonder how a single gt40r would compare with that.

 

[UZZ30-Québec]

ohh man, nothing below 4700RPM with the supra... BOOOOOOOOOOOOORING!!!

I'd say, go single and ball bearing. You can't have a 1000HP capability turbo setup and quick spool, however the amount of turbos you have Except in 3 cases

1- you are running a sequential twin turbo setup (spool only 1 then spool the other)

2- you are running 2 different size turbos an redirecting exausth system with a butterfly (similar to the sequential)

3- you're going Twin-charged with a M112 for the 1st 400HP to spool the big turbo then the turbo helps the supercharger to feed the engine. (or in that case you could go Vortech or Rotrex to reduce heat generated by the supercharger.)

 

[stevechumo]

I think there is a misconception that twin will spool faster. Its all depends on the size. Two T88 would not spool faster then a single T88. I think we have put this in mind when u do twin turbo. Just make sure you divid your engine size into two. It will get half of the exhaust gas and half of the heat. So for a twin turbo 4.0 its literally means two 2.0 engines. I am not leading toward either one, but just to open up some points.

Very true.

 

[WICKED SC400R]

I have driven a GT42- which one ar you looking at? because there is a GT42-76mm~1200hp, GT42-80mm~1500hp and GT-47-88mm. the 88 is good for 1700hp.

I drove a Supra with a GT-42 76mm and it wasn't any more laggy than the TO4R 67mm with a .96a/r housing on it. WAAAAAAY more power. Whoah. The 67 was much more fun to drive than the 76 even with less power.

If I were you, go with a sequential butterfly turbo system. full boost 2500rpm first turbo, still make 1300hp top end. Your spool depends a lot of the gas you using, the person who tuned it and how you drive. the 76mm GT-42 would spool at 5500-6000rpm on 91 octane but when Justin nenni tuned it on the 100octane, the car spooled at around 4700rpm with the exact same setup. Redline was 8500rpm. I believe a built 1UZ could rev to 11,5K. Much of this was attributed to advanced timing with higher octane gas. A stroked 1UZ should have no problem with the GT-42 76mm to spool around 3K. A 4.0L 1UZ should be full boost around 4K. That's not bad when you can rev to 9K+.

I was going to use a dual port 76mm anti-surge turbo. I have a e-flapper mod that could cut the spool down on a single to 1500-2K with the 76mm... we'll see.

Guys don't worry about lag with big turbos, I was like you until I drove one. If the car has a good light flywheel, speed density airflow(no maf), big throttlebody intake, there really is no such thing as lag if you know how to shift.

What are you using for ECU?

 

[deathblow]

so what would be my best bet in turbo, if i want about 1k Hp but on a single turbo???

 

[4000GT]

Both of those turbos are total overkill. A more realistic twin setup would be GT3076R's.

Lag on big turbos sucks... a lot. The problem comes when you shift and the turbo has to spool... again.

A good light flywheel is probably the worst thing you can do, all the rotational mass starts to vanish when shifting and the revs drop very quickly. See the point above why this is bad.

 

[Nick M]

I don't have the calculation, but I am not sure if the twin GT35R would spool faster then a single GT42R. Remember you are running one GT35R with 2.0 liters or in my case would be 2.35 liters or you can run one GT42R with 4.7 liters. I wonder what is the spool time of a WRX (2.0 engine) would do on a GT35R.

Here is a GT42 dyno on a 3.0 liter Supra (24 psi). The graph below represented a 3.0 liter. I am not sure how would a 4.7 liter would look like, but I am sure it will alot sooner then 3.0.

The GT35R has shown great all around use on the 3.0 7M Supra. I think it could possibly choke the V8 at high use. It will spool quick. For all out racing it might not work, but it sure would be a bitch on the street.

Your idea about the twin is correct. Twins do not help spool for the most part. You are only getting half the airflow. Turbo design and displacement effects spool more than setup.

 

[GSMnow]

So you want to make 1000 hp. OUCH, that is about 100 lb/min of air flow. Even ay 4.7 litres, at your 6,500 rpm that requires 35 psi of boost along with a good enough intercooler to get the temperature down to earth and some density back. You will either have to rev higher or flow better than your 80% VE figure to make this realistic. You will certainly have to run race gas to make this work. To make it reliable at 35 psi of boost and 100 lb/min of air flow, you need twin Turbonetics T61's
http://www.turboneticsinc.com/cm_t61.htm
and even that is seriously pushing the limits. Now raise your revs to 8,000 rpm and port the heads, big valves, wild cams, and whatever else it will take to get your V.E. up to 90% and it becomes a bit more feasible. At normally aspirated, this gets you up to 598 cfm out of your 4.7 litres. Now you only need 21 psi of boost to make 1000 hp. Assuming a perfect intercooler of course. Now a pair of 60-1 or 62-1 Turbonetics turbos does the trick nicely. This is only a 2.4 pressure ratio instead of a 3.4 pressure ratio. the required turbo rpm is far less as well, and the efficiency is alot higher as well. Here is the 62-1 flow map.
http://www.turboneticsinc.com/cm_t4621.htm
I know of a Mustang 5.8L (351) that runs twim 60-1's and makes over 1100 hp on a dyno. He has run 9.8 1/4 mile times on cheater slicks and the car is a convertable that weighed in at 4100 pounds at the track.

Of course, ball bearing 62-1's run $1528 each MSRP.
http://www.turboneticsinc.com/downloads/pricelist/Turboentics 2006 Price Sheet.pdf
Go to page 8 for the big turbos.

My Celica's 2.4L turbo motor ran a lowly plain bearing T3/TO4E-60 trim, but with only a Stage 2 .48 a/r exhaust side that they don't even list anymore. I should have run the 46 trim (that they do list with my small exhaust side) , it would have come on boost much better. I was in surge on the 60 trim until 4000 rpm. Even rolling around 3000 rpm and punching it, you could almost count one-one thousand, before it reached 10 psi of boost. It was a fair lag that became annoying in autocross racing.

Gary M.

 

[WICKED SC400R]

Flywheel = Spool? huh?

Both of those turbos are total overkill. A more realistic twin setup would be GT3076R's.

Lag on big turbos sucks... a lot. The problem comes when you shift and the turbo has to spool... again.

A good light flywheel is probably the worst thing you can do, all the rotational mass starts to vanish when shifting and the revs drop very quickly. See the point above why this is bad.

This is where book smarts end where reality begins. I apologize first and foremost for sounding cocky or arrogant, that is not where I am coming from, but when a lightweight flywheel alone drops .5 seconds of my time on road course, autocross or drag all that "theroretical" crap goes out the window. The less weight on rotational mass, the faster the acceleration and hp buildup is. The car with a stock flywheel was slower to rev, slower to react, slower throttle response, slower to react to the other inputs other than engine, SLOWER TO BOOST how can you argue that is the worst you can do?

If it's the worst you can do why do ALL racecars have lightweight flywheels- INCLUDING THE TURBOCHARGED ONES? There might be an exception here and there, but that makes no sense whatsoever. The only reason the factory puts in a heavy flywheel, is the ability to CRUISE on uphills, making the car SLOWER TO CHANGE SPEED and also make taking off the start easier for a NOVICE. THAT is the majority of driving that car will see over the period of the car's life, hence why they would tune the car to the most likely driving pattern, with the most likely driver over the car's life.

As a performance enthusiast, our passions drive us to modify our beloved cars to elevated performance levels and also driving them beyond the factory tuning hence why aftermarket is a multibillion dollar industry.

Aftermarket lightweight flywheel can not physically make the car any laggier, it's actually impossible. Things that affect spool: heat, displacement, head flowing characteristics, design of headers, turbo housings and exhausts, and especially gas used and tuning. Flywheel is not one of those factors. You don't have to change the "tune" of the car changing the flywheel.

Yes, the revs drop more quickly, and yes, if you are off your game as a driver, it will fall out of boost more easily. But the same token, you will have more control, and the car WILL accelerate much more quickly than a heavy flywheel when you can drive it that way. Which is imperitave when we are racing against domestics, with huge displacements and light flywheels. To beat them you have to play their game better than they do.

IMO, Flywheel is an issue of driver skill than spool or car being laggy. :drillsergeant:
As we modify our cars we are "supposed" to modify (improve) our driving skill too. :tapedshut:

 

[Lextreme II]

Man, right now I really thinking of a Big Single instead of two. Less complication and cheaper too. I wonder if a GT42R would fit. What do u guys think?