When An Rb Is Just Too Big....

[scathing]

Got the ticket right here...take 2 suzuki hayabusa engines and turn it into this 2.6 litre to 3.0 V8 that turns to 10,000rpm.

...Or if your soft just the H2 engine.

http://www.h1v8.com/page/page/1562068.htm

Or a Powertec motor. They also do gearboxes and drivelines.

http://www.powertecracing.com/pdf_downloads/v8engine.pdf

Turbocharged KA20 would haul ass and rev to 9000rpm

The K20 is an east-west motor. That said, if its being mated to a GT-R box it should be less of an issue.

[Race__24]

Well I think a 13b wins, either turbo or ported, there are a lot of good suggestions but a 13b is easy to come by and relatively cheap.

Besides, I can always change my mind later as I'm only at the designing stage.

Thanks for all the suggestions

Aaron

[warps]

You won't go too far wrong with a good injected 13B. If you can pick up a Renesis and 6 speed out of an RX8 then you'll have a good package with plenty of potential (porting is basically Peripheral Port at high revs). The 6 speed has nice close ratios from 2nd to 6th, so a lot of guys use them in rally cars. First gear is a bit useless on dirt with a super low diff, but perfect for driving the car onto the trailer if you have an angry clutch.

A ported S4/5 RX7 motor is apparently the ultimate, according to the IP guys (but they're not allowed to run PP). If you have class restrictions, the 13B will put you in the 2.0 - 2.5L category. Add a turbo and it pushes you out to about 4 litres - if you're racing in any CAMS type events.

[scathing]

Well I think a 13b wins, either turbo or ported, there are a lot of good suggestions but a 13b is easy to come by and relatively cheap.

I thought you didn't want a heavy engine? Rotaries aren't light. An SR20DET weighs less than a 13B TT.

If you can pick up a Renesis and 6 speed out of an RX8 then you'll have a good package with plenty of potential (porting is basically Peripheral Port at high revs). The 6 speed has nice close ratios from 2nd to 6th

It's got 2 overdriven gears. The ratios aren't that close.

[warps]

I thought you didn't want a heavy engine? Rotaries aren't light. An SR20DET weighs less than a 13B TT.

That's the turbos, intercooler and all that crap that adds to the weight. A NA rotor is light and compact for the power it puts out. No featherweight, but certainly nowhere near as heavy as the RB lumps.

3.5 alloy V8 is another fairly compact light engine. Stock they were poo, but again parts readily available and 350hp not that difficult.

It's got 2 overdriven gears. The ratios aren't that close.

Not compared to a proper CR box obviously, but then wont cost you $4-6k either. For a factory mass produced box that will bolt straight up to the 13B, they have very close ratios. Who cares how many overdriven gears it has? That can be fixed with diff ratios.

Yes, if money was no object, then you'd go some fully hektik sequential job for eleventy one dollars. As I said, quite a few rally guys are going for this option and loving them. Having rallied a rotary myself, I know how important a CR box is with a peaky engine in gravel (specially if you have a well sorted rear end and plenty of traction). For these boxes to be working so well in rally rotors, the ratios obviously aren't too bad. Again, I am NOT comparing to a *proper* CR competition box.

I'm offering a very effective option for a realistic budget. For the same money, you'll struggle to come close in an overall package which fits his requirements. I'm not a blind rotary tragic, but I can see their benefits.

[scathing]

That's the turbos, intercooler and all that crap that adds to the weight. A NA rotor is light and compact for the power it puts out.

...and not the cast iron housing?

Fair enough a NA rotor will be lighter than a FI one when you delete all that plumbing, but if that just brings the weight down to around SR20DET levels (or lets say a 4AGZE since those engines seem really popular in Clubmans) will a NA rotary be able to deliver the same power (both in terms of peak, and area under the curve) as the I4s?

3.5 alloy V8 is another fairly compact light engine. Stock they were poo, but again parts readily available and 350hp not that difficult.

Would it be any bigger / heavier than, say, a VQ? There are some US-based FM platform cars that run AWD with an active F<->R torque split (which seems to be one of the OP's requirements) so this could also be an option if a small V8 fits. Performance bolt-ons that couldn't carry on from the donor car anyway (exhaust, intake) would give him 180-190rwkW.

I'm not sure what the ratios are like in the AWD manual box, but the 2WD manual box runs 5th gear at 1:1. Which may not have been entirely necessary when you consider how torquey the VQ is.

Who cares how many overdriven gears it has? That can be fixed with diff ratios.

I know how important a CR box is with a peaky engine....

There's the rub. The diff ratio only affects the ground speed. The ratios control how far the RPM drops on each gearchange. If the engine is peaky, that long drop can drop you off the torque curve. It doesn't matter what the diff ratio is.

The shorter diff ratio means you spend less time waiting to get the RPM back up into the engine's sweet spot, but you'd be better off not having to wait at all.

Anyway, if he wants to use R32 GT-R running gear does that mean he needs to keep the GT-R gearbox? I can't remember how drive is sent to the front wheels. How would the ratios from that box match up to a RENESIS engine's power delivery?

[Race__24]

I'm hoping to keep the gtr box. I'm a CNC machinist by trade so making stuff fit shouldn't be a problem.

The rotor may not be the lightest engine out there but will give me a low center of gravity as I'll tuck it down as low down as possible. I haven't looked at the shape of their sumps yet but I'll probably be making something custom anyway. I'll try and find some CAD models for the 13b somwhere.

[warps]

There's the rub. The diff ratio only affects the ground speed. The ratios control how far the RPM drops on each gearchange. If the engine is peaky, that long drop can drop you off the torque curve. It doesn't matter what the diff ratio is.

The shorter diff ratio means you spend less time waiting to get the RPM back up into the engine's sweet spot, but you'd be better off not having to wait at all.

Anyway, if he wants to use R32 GT-R running gear does that mean he needs to keep the GT-R gearbox? I can't remember how drive is sent to the front wheels. How would the ratios from that box match up to a RENESIS engine's power delivery?

Yeh, that was kinda my point. The RX8 box only has one overdriven gear as per the table below (early RX8, not the current model)

1st 3.76

2nd 2.269

3rd 1.645

4th 1.187

5th 1

6th 0.843

As you can see, 2nd to 6th are very close for a factory box (with a useless 1st). Even the 6th gear is only slightly overdriven (the turbo boxes are 0.76 something). In fact, the early RX8 boxes are closer together than the Albin dog box set for the S4/5 gearbox (which I gather is made for big torque turbos)

I see that the current model ratios shown on the Mazda website are a lot wider than that. I don't know when the ratios changed, but the early stuff is what you'd be getting if you were looking second hand.

I know that if you have a wide spaced box, a low diff can help a little (effectively the gears are closer together in higher gears, so a low ratio diff will help to take advantage of this). However, the effect is only very marginal.

I dare say the GTR gearbox standard ratios would be poo with a track rotary. The only saving grace may be that the car is so light, it might not matter what gear he's in . I found the biggest problem in the gravel was trying to keep the wheels spinning. If the engine started to bog down (very easy with a 51 weber on a 12A) the ratios were too far apart to keep the wheels spinning, specially with new rubber. Once you tore the tread off the tyres, it was no problem keeping the rear wheels spinning.

If he wants to retain the 4WD capabillity, then yes that gets a little more complex. For the extra weight and complexity, as well as driveline losses, I would expect that a simple RWD setup would be the fastest way to go.

As to the weight of the rotary - yeh I said that they're no featherweight, but their overall packaging is compact, making them very effective in terms of hp per volume (physical volume, not swept volume which is a whole separate discussion). If CAMS factors into this in any way, then the capacity advantage of the rotary may be of benefit. If that has no bearing, then yeah, go nuts (and I point him back to my original suggestion of a 500hp L98).

[Sarumatix]

Surely what you want is a VQ.

[Race__24]

Will look into the VQ some more, might be easier to keep the gtr box.

What different cars did it come in?

Edited February 4, 2010 by Race__24

[Race__24]

The VQ looks pretty tall

[scathing]

Yeh, that was kinda my point. The RX8 box only has one overdriven gear as per the table below (early RX8, not the current model)

That's alright then.

I can't remember when I checked, but I recall seeing that Mazda Australia's RX-8 specs had 2 overdriven gear (like the MX-5, another car that should have left the factory with a close ratio box).

If the mass isn't a problem, packaging a RENESIS would be the best in a car this small. The relative lack of torque doesn't matter that much when the car weighs so little. The only potential issue is the AWD grip bogging it down off the line, but once its rolling I doubt it'll be a major issue.

[mad082]

That's alright then.

I can't remember when I checked, but I recall seeing that Mazda Australia's RX-8 specs had 2 overdriven gear (like the MX-5, another car that should have left the factory with a close ratio box).

If the mass isn't a problem, packaging a RENESIS would be the best in a car this small. The relative lack of torque doesn't matter that much when the car weighs so little. The only potential issue is the AWD grip bogging it down off the line, but once its rolling I doubt it'll be a major issue.

the lower torque would probably be a good thing. in a car so light the last thing you would want is a bucket load of torque coupled with AWD (unless bias was quite a way to the rear). you'd sneeze and jab the throttle a bit as you sneezed and spin off the road and end up upside down in a gum tree 300m away from the road, lol.

[scathing]

the lower torque would probably be a good thing. in a car so light the last thing you would want is a bucket load of torque coupled with AWD (unless bias was quite a way to the rear).

Well, he wants to use an R32 GT-R drivetrain.

[mad082]

yeah i saw that, but it was story time so i just went ahead with my story

[Jack_Sky]

I'm looking to design up a small roadster type thing, similar to the small kit cars you see getting around but I'm going in a bit different direction than most in that I want to use R32 GTR running gear with shortened axles and drive shafts etc. My problem is that the RB26 is just too tall for what I want to do, and to be honest it's too heavy as well.

The main problem I have is size, I want something that is short in height and length so the car doesn't end up huge.

Ideally a small ally NA V6 would be great, but I have no idea what's out there. I was even thinking a rotor because they are so small but I think I would prefer something with a little more torque. I'm not too fussed if it's NA or turbo but NA would be easier. I'm thinking around the 230kw mark, which should make for a quick car.

What can you people think of that fits the bill?

Cheers

Aaron

would be hard to find a small na motor with 230kw... even a v6 will be big..

i reckon go a 13bt, small and very powerful... lacking in the torque yes, but in a car that will most probably be very light will it need alto or torque?

or and sr20det.

[funkymonkey]

wouldn't a GTR AWD drivetrain just weigh the car down? its not exactly the most lightweight AWD system, I'd ahve thought an EVO or Subaru system would be far more effective in a car that light.

[lachlanw]

^^^^ he has already said he doesnt want a shit lsd based understeer i mean Awd system

[Ruffels]

http://www.toymods.net/forums/showthread.php?t=18227 <---- worth signing upto toymods to see!

1uzfe all alloy V8 into a 1970's ta22 celica with gtr awd running gear modified to suit!

[Hank Scorpio]

CA18DET with a stroker kit then prepare for mad respect.