Hello everyone. I just wanted to ask anyone to chime in and let me know everything they know about these turbos. I have searched and cannot find much info on them. Tell me everything, like what kind of motor build should I have on my 3rd Gen to run this turbo. I do drag race, and do highway runs, and I am not afraid to run some boost. My car will not be a drag-only car. I will drive the car on the street whenever I feel like it. Please, just let me know my options on the different ARs of this particular turbo and if I can get an Anti-surge compressor housing. And, on each different motor build, when can I expect boost or full boost(at what RPMs). What is the ~power output of this turbo on each engine build? Anyway, any info will greatly be appreciated, because this is the turbo that I have ultimately decided to go with for now. Thanks
Dee
Universal, GT42R, 1200hp, 76mm Comp Wheel - Ball Bearing, GARR GT42R-76
run about 3k and HUGE turbos. i think a forum member may be running one already.
Thanks razorback. Anyone else have more to add?
Dee
Xcessive is running one. Search his name. He made some nice numbers with it. Good luck on the streetability though.
Oh, I do understand that it will not be the most fun car to drive on the street, but I will be driving it anyway.
Dee
Xcessive is running one. Search his name. He made some nice numbers with it. Good luck on the streetability though. The GT42R that Xcessive tuned is a 100% street car. Spool isn't as bad as people would think. But when you do hit boost, hold on:)
LT1-7: Yeah, that's what I was thinking. I am ready for that boost to come on strong. At least I think I am. GT35R is just not enough. Hehe
Dee
Xcessive: Do you have anything to add to any of this?
Dee
There is a stock port/sleeve 20b on here that has the regular Gt42 that gets 8psi by 4,500 rpm's. I think it had the 103mm compressor and A/R was 1.15. This makes me wonder how much faster it would spool with a port job and the ball bearing version? Anyone want to take a guess? I'm thinking 8psi could come by 3k.
Yeah, that would be nice. Now if only I had a 20B to go along with it.
Dee
What is your goal? Most likely a T66/67 is a better choice. There is ALOT of custom Fabrication invoved in a 42R. If you were going that route, Magnus motorsportshas already done the work, and has a kit that retails 5-6K last time I looked. Try a ~5" exhaust, for starters. Unless you have Racelogic TC, or 335 R compound tires, the car will be almost undriveable. Tyson can comment, but you end up using half the turbos potential, and have to deal with tons of custom work to make it fit. By way of comparison, a 66, 67(TO4R) can make 600rwhp with the larger AR hotsides quite easily, and have about the same response as a 42R. Figure another 10K at least in hardware to support that sort of power, then add labor. Properly suspensioned, and driven by someone that can drive, a 450rwhp 7can run 10s all day long. I am assuming you are concerned w/drag, since a 42R is not good for much else unless you are a master of innovation, and fabrication. Point is, it is very exoensive overkill, and your manifol/exhaust/IC piping will not be compatible w/anything else if you don't find that you like it after sinking 20k into a set-up. am assuming in these numbers you are starting with a stock vehical. good luck, Carl
Here you go. That is an absolute steal.
Whatever the guysays, figure complete loss of all meaningful traction once boost hits. if iit is already sold, ask him why he sold it. Carl
Carl, thanks for the info. I already have an Apexi Power FC, Fluidyne Radiator, and I have the money to get my motor built. What I need to be able to decide, is what kind of motor build I will need to get the best performance out of that turbo setup. I will be buiding the motor first and driving around and breaking it in with the stock twins for a little while, then once I have enough saved up, I was wanting to go the single turbo route. Just wanted to go with the GT42R. Thanks again.
Dee
PS. If you have anything else to add, please feel free.
With a ported motor you can expect to see both higher dyno numbers as well as better spool. Honestly for this turbo I wouldn't port my motor any smaller than a half bridge. No offense to you Carl, because I know you know your stuff when it comes to road racing, but if you want to know honest information from someone WHO HAS experience with this turbo, you should call Sean at ASPEC tuning.
- Steiner
Here you go. That is an absolute steal. Thats a big freakin turbo !!!!
Yes, it is. And I will hopefully be going with one.
Dee
With a ported motor you can expect to see both higher dyno numbers as well as better spool. Honestly for this turbo I wouldn't port my motor any smaller than a half bridge. No offense to you Carl, because I know you know your stuff when it comes to road racing, but if you want to know honest information from someone WHO HAS experience with this turbo, you should call Sean at ASPEC tuning.
- Steiner No offense taken, Magnus was running a 42R before Sean was born (JK). Notice I refered him to Magnus, (the first I know of to get one running, and performing properly), and to Tyson who runs one. Again, my thought is why go to such fabrication lengths, when you can get the HP that most want out of this turbo with off the shelf parts? If he is building a 650-900hp car, that is different, but for 500-600 this is a pretty extreme way to get it. Problem is, the mani/IC pipes/exhaust will not work with anything else. A T51 can get it done and use off the shelf parts. A GT74/76 Q/S/R trim will do it as well. All these have 4" V bands(except maybe the 51 which is smaller), and use a standard T4 flange. Not to mention they are a dime a dozen on Supra forums, as the Supra guys have pushed past 850-1000rwhp, and are looking for more. Carl
Sorry I didn't see that you recommended Magnus, he is definately one to contact. I agree that other turbos could be used to achieve the same horsepower number with less effort. But if he has his heart set on 42, I say go for it.
- Steiner
Right, I was just making this thread to find out more about the turbo itself mainly and I will probably be calling Sean at A-Spec soon.
Dee
We have one on a FD with a large street port and its a blast. The car is like a shifter cart.
This on only 18psi. Also we run 305-25-20 rear p zeros in stock wheel wells and traction
is not to bad. We like this car over any other RX7s we have built for fun factor. What we consider street differs from other people because we run 4" exhaust which is pretty loud,
so is the stereo. Just my 2 cents. Manifold by Sean, ASPEC
Ralph
Ralph: Well, I mean streetable as in capable of driving on the street. I don't care about loudness or anything like that. 4" exhaust is fine with me. Can you email me with a little more description about this street car, like the other mods done to the car, so I can get an idea of other things I will need? Also, what exact size ARs does this turbo have, and what are the spool characteristics of it? Any extra info will certainly be appreciated. Thanks in advance.
Dee
We have one on a FD with a large street port and its a blast. The car is like a shifter cart.
This on only 18psi. Also we run 305-25-20 rear p zeros in stock wheel wells and traction
is not to bad. We like this car over any other RX7s we have built for fun factor. What we consider street differs from other people because we run 4" exhaust which is pretty loud,
so is the stereo. Just my 2 cents. Manifold by Sean, ASPEC
Ralph Ralph,
I got your manifold the other day and started sanding on it. It's a great looking piece and can't wait until it's fully sanded and port matched. It'll look really cool with my custom upper plenum.
I got my GT42 in today and it's going in the car within the next couple of days. I'll send you some pics of the new setup so you can see what you think.
Look at my sig for an old pic of the car....
talk to ya soon,
Elliott
silvr94r2: That is a nice looking car you've got there. I can't wait to see the GT42 pics.
Dee

He only posts pictures of his 3rd gen but never posts pictures of his 2nd gen.
So, I'm doing him the favor. :lol2:
Why is the area code not an STL number???
EDIT: nevermind I thought Busted7 was Ryan Scott
whoa. Now my penis is hard.
I need to finish it its only been sitting for 3 years! I was stupid to put the blower on it even when it ran it only made 25 lbs at 9000.00 rpm's but i did drive it to the portapot in the pits looping like a big motor! I should know better but suggestions will be appreciated. Thanks!
got any more pix of that thing Charlie?
That car is fuckin nasty!!! Any pics of the intake manifold or any other info on this car???
No more picts right now but ill try and get some. The intake was a pain lower intake is a 3rd gen and upper is a secound gen. The motor is athird gen 3 mill ported motor with a gslse front cover with dist. I made the 653 supercharger an oil bearing style with drain back and built the lower plate for the blower and o-ringed it to seal. The bearings would not hold up to 18,000. rpm's as its driven 2 to 1. Plus a 2800 stall auto wont cut it either. There was alot i just didnt know but i built it anyway becouse i didnt know who to ask. Its a narrowed 9'' 4 link with 5:14 spool 29.5 10/5w slicks on bogart 12'' wheels and a set of the only bogart 3.5'' front wheels with 3'' back space. I need help with the proper set up and as always the money! Its alchahol toliet would he hard to turbo maybe? It just sits as i have put a lot of money, sweat and yes blood.but i just cant sell it.
No more picts right now but ill try and get some. The intake was a pain lower intake is a 3rd gen and upper is a secound gen. The motor is athird gen 3 mill ported motor with a gslse front cover with dist. I made the 653 supercharger an oil bearing style with drain back and built the lower plate for the blower and o-ringed it to seal. The bearings would not hold up to 18,000. rpm's as its driven 2 to 1. Plus a 2800 stall auto wont cut it either. There was alot i just didnt know but i built it anyway becouse i didnt know who to ask. Its a narrowed 9'' 4 link with 5:14 spool 29.5 10/5w slicks on bogart 12'' wheels and a set of the only bogart 3.5'' front wheels with 3'' back space. I need help with the proper set up and as always the money! Its alchahol toliet would he hard to turbo maybe? It just sits as i have put a lot of money, sweat and yes blood.but i just cant sell it. Thats tight man! Please post up more pics especially the motor setup.
thats badass, what size is the blower??? Do you think you would see better results with a twinscrew blower?
Its smaller than a 671 its a 653. I have never seen a blower rx7 that has been succesful. Ive seen some for show and a first gen that blew up but thats it. It just needs turboed and maybe a trans change. Ill get more picts thanks for the intrest!!

I kept trying different things to see what the car wanted. I got a couple good data logs and figured out a lot of info. Something went wrong on every pass i made and I'm still having boost control issues (but i know how to fix them now). The last pass i made was the best but i forgot to take my finger off the two step button so i hit the rev limiter in each gear :wallbash: . A few adjustments and a little more seat time and 10.7 on pump won't be a problem :icon_tup: . The transmission is pure sex and the car handled flawlessly. Next weekend C16 goes in the tank and we will se what she can really do :shocking:.
The one pass that i ran the white mustang would have been in the 10.8 zone had i not rolled trough the lights :bigthumb:.
http://www.youtube.com/watch?v=RIA-bSngxOY
great runs but i would get a new camera man/women :rlaugh: :rlaugh: :rlaugh: otherwise the car sounds really good!
great runs but i would get a new camera man/women :rlaugh: :rlaugh: :rlaugh: otherwise the car sounds really good! :lol2: Yeah, he had other things on his mind.:101384_l::buttslay::ky::bj::kiss::69::whip: I guess it's had to film with a hard on.
Looking really good. You still have alot of time to drop when you git her all dialed in.
nice runs man.
Hell yes ! Congrats Allen !
How much boost are you able to leave on ?
Got a time slip to post ? I'd like to see the increments.
Sounds very good. And that transmission, sounds like it shift nice and fast. Very niice brother.
Hell yes ! Congrats Allen !
How much boost are you able to leave on ? All.
Got a time slip to post ? I'd like to see the increments. Sure, let me scan it.
Sounds very good. And that transmission, sounds like it shift nice and fast. Very niice brother. Oh yeah, i love the trans and shifter!!!
the car sounds nice....
Got a time slip to post ? I'd like to see the increments.
Sorry, my scanner took a shit.
R/T .5952
60 foot 1.5465
330 foot 4.4422
1/8 6.9004
1000 ft 9.0544
1/4 10.9038
:icon_tup: :icon_tup: Wishing i was there watching. Good racing!
your car is starting to take on a personallity.. always a good thing in my book. congrats...
Thanks Ito. It's great the amount of attention the car gets. Every time i stopped someone would come up and ask about the car. At one point a guy sprinted from the food line to yell at the top of his lungs "i love your fucking car". It was a great day overall. I hope next weekend turns out as good.
Sorry, my scanner took a shit.
R/T .5952
60 foot 1.5465
330 foot 4.4422
1/8 6.9004
1000 ft 9.0544
1/4 10.9038 Watching the video, was the car bogging a little bit or spinning the tires ?
Have you got the suspension dialed in pretty well ?
Watching the video, was the car bogging a little bit or spinning the tires ?
Have you got the suspension dialed in pretty well ?
One pass there was a lot of water on the track and it spun bad off the line and in second and third. The rest of the passes (without going into great detail) the car would launch and then the boost would oscillate until it hit the target boost. It would launch and then the boost would drop and begin to climb.
The car hooked flawlessly and went string straight, i have no reservations about running C16 in it now!!!
your car is starting to take on a personallity.. always a good thing in my book. congrats... Yes it is and the driver also.
That car is begging for some more boost and methanol! :lol:
Nice build, glad to see you're really enjoying your project!
car is looking really good allen , really good:icon_tup: :icon_tup: :icon_tup:
Nice man, keep up the hard work. It's paying off.
Dee E.
Yes it is and the driver also. :lol:
You think I'm bad now? Wait till i run a 9 :shocking:.
You think I'm bad now? Wait till i run a 9 :shocking:. sign my hood ! :shocking:
sign my hood ! :shocking: $50
love da car man
$50 :lol:
Thanks everyone. I am really glad i built this car. I have met a lot of interesting people and made a lot of friends in the process. Not to mention this car is more fun than a motorcycle!!!!!

On the track, the only time I use left foot braking is when I'm exiting in the same gear that I'm entering in, in order to shorten the transition from brake to gas. I sometimes wonder, how do you efficiently apply left foot braking when coming to a corner that requires a downshift or two. With a traditional manual gearbox, how would you properly downshift while braking?
how do you efficiently apply left foot braking when coming to a corner that requires a downshift or two. With a traditional manual gearbox, how would you properly downshift while braking? You don't. ;)
I've observed a lot of professional in-car foot cams over the years and most professional "Sports Car" drivers don't use left foot braking that manner. I highlight sports cars as prototypes and F1 style cars are completely different. ;)
Most of them just use the left foot to prep the brakes before the braking zone or to settle the car on a bumpy track. Here's a good video of some footwork in a Porsche (even a little double clutch action):
http://www.aimsports.com/video/policastro2.mov
Some good footwork:
http://www.youtube.com/watch?v=CWMuAAd24ao
You don't. ;)
I've observed a lot of professional in-car foot cams over the years and most professional "Sports Car" drivers don't use left foot braking that manner. I highlight sports cars as prototypes and F1 style cars are completely different. ;)
Most of them just use the left foot to prep the brakes before the braking zone or to settle the car on a bumpy track. Here's a good video of some footwork in a Porsche (even a little double clutch action):
http://www.aimsports.com/video/policastro2.mov Strange, he likes to go 4-3-2 with only one blip of the throttle.
Coming off the long straight in the beginning of the Road America circuit, he goes 6-5-4-3-2 with only 3 blips of the throttle. Then in the short straight into the left hander, he goes 5-4-3-2, with only 2 blips of the throttle. It's like he couldn't move his feet fast enough for 3-2, either that, or he doesn't car, and his flywheel is really really light and his clutch is really really strong. No double clutching either, he forces the engine to spin faster by double tapping and slipping the clutch from 3-2.
I don't understand, if you're going to rev match 3 shifts, why not rev match the 4th shift as well?
I definitely use the left foot brake to stabilise the car when I run the simulations (i.e. video games). On the track though, my car doesn't have enough power nor is my suspension so stiff that I have trouble on bumpy surfaces, though I imagine next year, I will have to start.
Last time I used left foot braking, I ended up spinning since I carried 10 mph more than normal. It was a very cold day and the rear tires slipped midway through the corner upon throttle-on. Wasn't very fun, but I feel that if I could get that right, I could cut down a lot of my lap time, since this corner in particular leads onto the longest straightway. The track was Lime Rock Park in CT.
Some good footwork:
http://www.youtube.com/watch?v=CWMuAAd24ao Wow, those clutches engage so fast, and the flywheels are ridiculously light! The amount of time on each pedal is so much shorter compared to when I'm on it in my car.
Keep in mind that the cars in those videos are using sequential transmissions. They don't really need that much of a blip on their downshifts. As you'll notice in the Mike Rockenfeller video that he doesn't use the clutch on the upshifts.
But back to you question, if you are downshifting and using a clutch, then you won't be left foot braking. :) That doesn't mean you can brake into the corner, and then as soon as your into the corner you quickly move your left foot back onto the brake pedal to finish the turn. There is a video of a guy doing this, but he basically just using the brake to correct too much throttle:
http://youtube.com/watch?v=R3O66igd0w8
If was wasn't applying so much throttle, he wouldn't need his foot on the brake. ;) I doubt he's gaining much by doing it. I 'debated' with the driver on another forum and he agreed that using the brake was for 'corrections' not necessarily for 'speed'.
I see what you mean, when I meant speed, I was referring to shortening the transition from brake to gas in corners where there is no need to shift. Also, the weight shift dynamics are subtly affected as well.
Are they sequential dog, or H-shift dog transmissions? I couldn't tell in the videos.
I see what you mean, when I meant speed, I was referring to shortening the transition from brake to gas in corners where there is no need to shift. Also, the weight shift dynamics are subtly affected as well. Well, if there was a substantial advantage doing it; the Porsche factory drivers would be all over it. You can also look up the V8 Supercars from Australia videos and you'll see the same use of left foot braking. IMO, unless you are in a clutchless car; there's not much use for it outside of what the professionals are doing.
Are they sequential dog, or H-shift dog transmissions? I couldn't tell in the videos. Sequential, IIRC.
Well, if there was a substantial advantage doing it; the Porsche factory drivers would be all over it. You can also look up the V8 Supercars from Australia videos and you'll see the same use of left foot braking. IMO, unless you are in a clutchless car; there's not much use for it outside of what the professionals are doing. I think the reason why more people don't is that you would have to practice braking feel on both feet and as well as properly transition left foot braking to right foot braking with out messing up. I guess people don't think it's worth the risk to potentially mess up in a pressure situation and put the car into the wall. Maybe the simpler way is the faster way.
Still, any advantage is an advantage on the track, no?
I do left foot braking all the time. It's easy to keep a cold engine running when you're too lazy to set the choke.
I think the reason why more people don't is that you would have to practice braking feel on both feet and as well as properly transition left foot braking to right foot braking with out messing up. I guess people don't think it's worth the risk to potentially mess up in a pressure situation and put the car into the wall. Maybe the simpler way is the faster way.
Still, any advantage is an advantage on the track, no? Mike Rockenfeller is (well was, he's an Audi Factory driver now) a Porsche factory driver. That's his feet in the YouTube video and you don't see him using it other than to set the brakes for turn and to steady the car. Now, I'm sure he does use it when he drive the Audi R10 LMP1 but as I mentioned above those cars are completely different animals than production based cars with clutches.
Basically, if you have to "think" about it, then you aren't being fast. i.e. if you are thinking about whether you should to use your left foot or your right foot for an upcoming turn, you are slowing yourself down. Like I said above, I'm sure those professional drivers would use it if it was worth it.
Sean Edwards, a professional driver http://www.seanedwards.eu/ , commented in another forum that there really is no speed gain by doing it. He said he does do it some on turns which do not require downshifts, but he said its just a preference thing.
Some good footwork:
http://www.youtube.com/watch?v=CWMuAAd24ao Nice Vid:icon_tup: . I tried left foot braking but I don't have the control over it like I do with my right foot.
For those sequential gearbox cars... they don't have to use the clutch on the downshifts. You can left-foot brake the car and blip the throttle with your right foot to engage the lower gears. Some drivers (rockenfeller appears to be one of them) likes the habbit of braking with his right foot and dipping the clutch on his downshifts (which is better for the gearbox especially during endurance racing.
0.02
I know, I was asking what one would do on a traditional manual gearbox
Left-foot braking is very useful to stabilize your car in a corner and/or provide smooth weight transitions. However, I believe that in conjunction with a traditional manual gearbox it will only be a viable option during a down-shift scenario IF left-foot braking is second nature to you AND your footwork is up to it.
Case in point: Walter Roehrl, the rallye legend:
http://www.youtube.com/watch?v=Ts29KKhKXds
Just my two cents as views clearly differ on this topic.
That's some bad ass footwork.
It's like I was saying, you have to switch back to your right foot to brake and downshift on the same time, but for corners that you don't have to shift on, you can brake with the left and drive with the right. You just have to make sure it doesn't make you slower, because you have to keep thinking about switching or not.
Left food breaking and manual gearbox makes me think rally racing. FWD rally drivers (and any other FWD driver) lives off of left foot breaking. FWD cars are nose heavy, consequently they understeer like pigs. If you left foot brake a FWD car it is sort of like pulling the e-brake. It helps compensate for understeer. You are essentially locking up the the back wheels and power overing the brakes in the front. Sort of like a Brake Stand on a RWD car. From my understanding of racing FWD cars you never take your foot of the gass. It is only a matter of how hard you are on the brakes.
In a RWD application shifting weight smoothly as previously mentioned is a major application. I supose you could also use it to induce understeer if you needed too (stabalize the car).