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SR20 V RB25de MX5 project

Wilso R32

By Wilso R32,
in Engines & Forced Induction

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Wilso R32 Contributor

Wilso R32

Posted
Posted

RITE.......................!

Need some "sensible" advice on wich engine to use.

Plan is I have an 2001 model MX5 on the way, lots of front end damage, but nothin I cant sort out.

At first I was planning to put a chevy 350 short block in there, but after the last one i ballsed up, im not gana bother!

Choices are,

Fairly standard sr20 or

Rb25de with performance throttel bodies conversion, high lift cams and mappable ecu upgrade.

Both engines are the same money, but wich will perform better?

not usin the car sor drag or drift or anythin, just a fast as fcuk street racer.

Always wanted a 2 seater monster, had an mr2 and cant afford a TVR so this is totaly my own thing.

Susspension setup is sorted one the engine is finished so the extra weight will be counter acted with the susspension package.

Another concern is the reliability of the engines,

SR20 is prone to bottem end nock, expensive to upgrade, and the extra heat of the turbo and fitting of the intercooler could make life extremly difficult.

RB25de is slightly bigger (understatement) and weighs more, but the upgrades i have on the shelf and I dont have the problem of the heat and intercooler, plus a 50bhp shot on Nos will see it fly!

Or would I be better of with throttel bodies on the SR20? better low end torque is a must in this project, Ive had turbo's and i have an RB30 R32 project on the go so this is purely for fun!

Any suggestions welcome!

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https://www.sau.com.au/forums/topic/57797-sr20-v-rb25de-mx5-project/
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DAN00H Mentor

DAN00H

Posted
Posted

why are you thinking of putting mulitple throttle bodies on the SR20? this will REDUCE it's bottom end performance. why not fit a turbo rotor? I'd steer clear of the RB, WAY too much work to engineer it to fit! (not to mention the weight balance - do you actually want to turn corners!?!?!).

The turbo motor will give you better performance. In Oz we have a company that builds these cars with the Lexus 4.0 V8 and a 13B turbo. Do a search for 'bullet mx5' and you might turn something up.

Good luck with it.

Wilso R32 Contributor

Wilso R32

Posted
  • Author
Posted
why are you thinking of putting mulitple throttle bodies on the SR20? this will REDUCE it's bottom end performance. why not fit a turbo rotor? I'd steer clear of the RB, WAY too much work to engineer it to fit! (not to mention the weight balance - do you actually want to turn corners!?!?!).

The turbo motor will give you better performance. In Oz we have a company that builds these cars with the Lexus 4.0 V8 and a 13B turbo. Do a search for 'bullet mx5' and you might turn something up.

Good luck with it.

Why? because im bored!

Were I work we have done a V8, and it was extremly long winded and we ballsed it up! Ive read up on the Bullet mx5, alloy space frame ect and cost 5-4 times as much as a new car.

Just lookin to do somethin different, Ive had turbo's and ive got my R32, so this is just for fun and probably wont be finished till late nxt year!

If they can get one to handle with a Alloy V8, then why would it be any different with the RB?

What about the lexus 2.5 twin turbo?...................................................

Roy Grand Master

Roy

Posted
Posted

RBs are cast iron blocks...SR are all alloy, so there would be the weight difference.

If your in the UK, throw a Rover V8 in there, cheap and punchy. A 250hp V8 belting out a great note, or just throw a turbo SR, i wouldnt bother with an NA SR, may as well just stick with the B6 Mazda engine

Wilso R32 Contributor

Wilso R32

Posted
  • Author
Posted

Ive got 2 cosworth engines in my garage! never even thought of it, nice one.

Maybe the RB isnt worth the hastle, either the sr20 or cosworth are worth considering.

I can get a rover V8 with a set of blowers for next to nothin, but after tryin the last v8 swap im not sure i can be bothered with the head ache, and it handles like a hippo on ice skates.......................

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