ScottH

Hello all,

I'm UK based and have a kit car that needs a new engine.

It was an ageing 4-cylinder Ford unit in there, but I decided I wanted to put something a little different in it, so after a little time thinking about it, I settled on a Renesis.

I picked up my donor car the other day - a 2004 6-port model. It had 55k miles on it and drives pretty well. It starts from cold and hot. It has a little panel damage, so I got it really cheap at auction (£700 / $1000).

My plan would be to strip the engine, transmission, and diferential, and transplant them all into my car. The finished weight should be around 550kg (1210 pounds)... less than half the weight of the RX8.

I understand how the wankel engine works, but I'm not fully up to speed with all it's intricacies... this is where I'm hoping you guys will come in handy!

I have no emmissions restrictions, so I plan to use the follwoing 'IDA' style inlet manifold parts from Racing Beat, so I can junk the standard inlet system and reduce the height of the installation.

RX-8 Engine Carburetor/Manifold Adapter Plate for RX8 - Racing Beat

Weber Intake Manifold 48/51IDA for 86-92 13B 6-Port - Racing Beat

I will then add a set of Jenvey 50mm 'IDA' injection throttle bodies...

TA body 50mm Single - Jenvey Dynamics

And then a standalone ECU.

I will also change to a lightweight flywheel.

I do not require a catalytic converter and there are no 'packaging' restrictions in my engine bay, so I can be as invetive as I like with the header design!

So that's kind of that!

I've also picked up a spare 6-port engine that I plan to pull apart, learn from, and then rebuild. I guess I could do with some pointers as to what to aim for in my rebuild. I don't want forced induction (230-or-so ponies in such a lightweight car is more than adequate). It seems to me that the induction and exhaust on the Renesis are quite compromised (?). Bearing in mind that I do not have to meet any emmission limits, would it be worth sealing the side ports in the spare engine and changing over to peripheral ports? Would the car still be reasonably reliable and would it remain civilised at low revs?

That's probably enough from me just now... I have loads of questions, but I'll ease into it!

Thanks for reading and I look forward to your input!

Carbon8

iTrader: (4)

Should of got a REW

Brettus

iTrader: (2)

Something that has become a big issue for conversions like this is how to oil the apex/corner/side seals . It has been established that if you use premix only , over a short period of time the corner seals will dig into the land on your exhaust ports .

You need to find a way to control and utilize the omp to get acceptable engine life.

ScottH

Cheers carbon... what would your reasoning be for the REW (bear in mind I'm a newbie!)?

Brettus

iTrader: (2)

1/ see my post above yours ....

ScottH

Thanks Brettus... I've seen that the aviation guys seem to be getting closer to cracking an RPM based OMP. I'd planned on taking my cues from them.

Carbon8

iTrader: (4)

Same reason most Rx8 owners wish they had one, in most peoples mind it was a much superior design, more reliable, more potential etc.....

REW was designed for power, RENESIS was designed for emissions.

ScottH

The REW doesn't use an OMP?

ScottH

Thanks... I'm off to google the REW LOL!

If it bolts up to the 6-speed Renesis transmission, then I can easily change!

I juts went for the Renesis as it seemed to be the one that made the highest NA power.

Carbon8

iTrader: (4)

If you need NA stick with the RENESIS, not sure what the end use of this car is.

For comparison,

REW; More engine management/ mod-ability present. potential for 350-400WHP @10PSI, not much reliability issues 80-100K miles

RENESIS FI; Only 2 choices for engine management/ mod-ability limited. Potential for 300-330WHP @10PSI, reliability drastically reduced 30-60K miles

ScottH

Yeah... I want to stay NA.

The car is purely for playing with on the highways and then the occasional track-day, so 'driveability' is very important.

A big toy!

ScottH

Just out of interest, what is it that makes the REW more reliable over the Renesis?

Brettus

iTrader: (2)

I meant .... the inability to rely soley on premix . But it seems you have that covered .

I think it would be a good choice if you can get that sorted .
As that RB manifold doesn't cater for the APVs- you will lose a lot of power under 6000rpm !

dannobre

iTrader: (3)

Renesis has side exhaust ports...and this configuration appears to be having issues with the heat and side seal life. As well as much shorter apex seals

The REW had a peripheral exhaust port...and less side seal issues with the heat

Power wise though the Remesis does well NA...and as long as it stays within the NA parameters it seems to be less of a problem. The issue is when we try and stuff 3-4X the exhaust flow out the 90 degree port....

ScottH

I don't mind a drop in low-to-midrange power (bear in mind the car is a lightweight and doesn't need much to get it moving). Am I right in thinking that the RB manifold would be likely to make more at the top end though?

ScottH

Thanks!

Brettus

iTrader: (2)

Highly unlikely - the stock manifold also has VDI (variable dynamic Intake) which gives the engine a nice little kick from 7200 on .

ScottH

Would there be any way to get better NA results from the REW? Can you mix and match some of the Renesis engine components with it to increase compression, etc?

ScottH

Thanks - that info could save me a bit of money! I would only be looking to junk the standard intake as engine bay height is my only restriction. If it all fits under there, then I can stick with it if there are no great gains to be had from going aftermarket.

I guess that really restricts my ECU choice though as there are a lot of valves and clever gizmos on the OE intake... you mentioned there are two that can do the job - any pointers on what they are?

RIWWP

iTrader: (2)

Keep in mind that you have an ECU on hand for no extra cost that can, and has, run that engine It shifts the electrical challenges to dealing with the other stuff, like wheel speed sensors, immobilizer, etc... but considering that you have the complete donor car, you have every module already paired with the ECU that is on hand and all of the sensors that go to those modules, so those challenges wouldn't be insurmountable. Tuning would be as simple an an AP or MazdaEdit.

Just something to consider.

ScottH

Thanks RIWWP. Are the AP and MazdaEdit both ECU piggybacks?

RIWWP

iTrader: (2)

No, they are flashing tools that allow you to edit the ECU tables directly and then upload those changes up to the ECU ROM.

ScottH

Thanks very much! I'll look into them!

Brettus

iTrader: (2)

But ................... has anyone ever run the ecu outside of an 8 before ?

RIWWP

iTrader: (2)

Not to my specific knowledge.

It's still a free option to at least try considering that the donor car has every component and sensor that the ECU is looking for already on hand. The challenges would be different than an aftermarket ECU, but comparing them, I would think that the challenges of using the factory ECU would be easier to solve and cause fewer engine reliability/driveability problems.