AdamL

Afternoon all.

I am from over the pond and looking for advice on my engine setup. My longterm goal is circa 350bhp. Now I know what to do to get that but I am being advised by people in the UK that's a silly goal, a torsen diff and 6 speed box will not last long at all and rebuilding the motor with forged internals is asking for trouble as it won't last long. They advise sticking this side of 280bhp and running a stock engine without opening it up!

Is that true about the diff and box?
I really don't understand how a rebuilt engine will not be up to the job. I can onlt think that these guys have had bad experience with poor built engines. I thought a well built forged engine would be almost bulletproof.

I am a little lost and just wanted some further advise before I proceed.

Braineack

iTrader: (62)

a DD with that power goal should not have issues with the 6-sp trans nor diff nor motor.

AdamL

Sorry, I should have said. It will be a 100% track car, stripped, made as light as possible etc.

Braineack

iTrader: (62)

motor will be fine. trans and diff will need to be monitored. See how Savington is handling it.

sixshooter

iTrader: (12)

I don't know how anyone could say that a forged engine would be less reliable than stock, unless, as you pointed out, it was poorly built. A poorly built stock one would likewise be unreliable.

I would use billet oil pump gears and a good aftermarket harmonic damper.

Edit: I think Sav is putting out 280-300 wheel hp on the track.

rharris19

iTrader: (41)

I wouldn't ask for advise from anyone that you have talked to previously over there again. Engines are not some magical mystical thing that once taken apart, can never be the same. If you don't feel up to the task, then have a local machine shop build the motor. Everything you are going to be puting in it will probably be new, so there is no real protential problem if done by anyone remotely competant. Have your cylinder head checked while you have it all apart too if you have a higher mileage motor.

Build your motor with these and you should have no trouble at that power level:
949racing or m-tuned rods
boundry engineering oil pump gears
supertech or wiseco low comp pistons
New quality water pump
New timing belt w/ new tensioners
New Felpro or oem seals all the way around


That can be true about the dick in a box, if you are doing some hardcore racing.

If you are driving it on the street you should be fine, but avoid doing too many launches on a drag strip if you don't know what you are doing as whele hop can hurt a torsen at those poer levels. Other than that they are pretty bullet proof.

AdamL

You have all more or less said what I thought. I didn't really believe what people were saying but after a few told me the same thing I did wonder what is so special about MX5 engines!
What is a harmonic damper? Thats a new one on me.

I will be building the engine, I have built 3 different engines before but not a MX5. Block and head will be checked by machine shop.

sixshooter

iTrader: (12)

This or similar:
http://www.summitracing.com/parts/ATI-918522

At those power levels for track duty I would recommend one. Our engines have some harmonics issues that can effect reliability at higher RPMs and higher power levels. It is cheap insurance.

+1 what RHarris said.

hustler

iTrader: (6)

Rharris is right. I've been tracking my car at 240whp with the 6-speed and it's fine but I'm very easy on shifts, soft with the clutch, and leave a lot of time on the table because of it...but I make it home every time.

I hope you have years and years of experience because a 250whp Miata is a handful, a 350whp car is a death-machine.

hustler

iTrader: (6)

The only problem with that thing is that it's a huge pain in the *** to instal and remove. suddenly a simple timing belt job requires pulling the engine to pull the balancer.

Braineack

iTrader: (62)

I'd still build my motor for a 250rwhp track car.

AdamL

I am 29, soon to be 30. Had a TVR, 2 MR2 turbos(1 @ 250bhp and 1 @ 300),Elise....
Been on track in quick cars too and just want something that is always going to feel very fast. I don't want to build something that in a year I am bored of and want more power.
I am sure many of you have been there.

hustler

iTrader: (6)

I own a Lotus Esprit V8TT, AMGCLS, and a 43' Prevost coach.

I didn't mean to imply that you weren't a good driver, but 90% of people don't understand how fast a 250whp Miata goes around the track.

As for the list of cars, 99% of this forum's track crew ****'s all over that list every weekend, and we do it on less than 250whp, on our out-laps.

Over 250whp on a track car is a losing battle and you better have a spare with you because you're on borrowed time.

AdamL

Hustler - only fair of you to ask. I can understand you asking too, there are far too many guys out there coming from a 1.4 engine and wanting a 300+bhp monster but not having a clue what that equates to in terms of speed. I have driven Caterhams and single seaters on track also so quick cars are not out of the norm for me.
Appreciate all the advice.

Why do you say that "Over 250whp on a track car is a losing battle and you better have a spare with you because you're on borrowed time."?

hustler

iTrader: (6)

Because the transmission is a wear item and half a dozen or roughly 90% of the 250whp+ crew have gone through several 6-speeds. Around here we gauge your masculinity and skill on how much faster you go than the SM record, or if you can best the MX-5 Cup record. I know a lot of "members" and instructors who drive C6Z's and Porsches that don't go as far under the record as we do. By "we" I don't mean me because I'm still learning and only standing up to peepee at one track on the schedule.

AdamL

What is your spec Hustler?
Did I read somewhere you are running ebay China rods?

It sounds like 250 at the wheels sounds like the upper limit of safe unless I win the Lottery, haha. At least that gives me a goal to build my spec around and go parts hunting.
At the moment I am going to strip, clean, hone my 1.8 engine and put back together with a 99 head and run it N/A till the turbo engine is built and ready to pop in. By this time I will have the rest of the car sorted and ready for the power hike.

18psi

iTrader: (76)

I don't track my car so take my input with a grain of salt, but: have you driven a 350whp miata? At all, whether it be track or street or whatever.
When it breaks loose (and it easily does in the lower 3 gears, and even more easily mid corner) with no electronic gizmos or traction control and a short wheel base its a job and a half straightening it back out without slowing down dramatically and ( I assume ) losing lots of time. Just my .02

AdamL

No I havent driven a 350bhp MX5 but I have driven enough that I can imagine what it's like. I am quite happy in a slide and comfortable to control it. People always moan how dangerous the MR2 is in the dry when pushed and leathal in the wet. I never found this, yes it would easily stick the back end out but it was always precdictable and easy to control.

miata2fast

iTrader: (2)

I would get a good balancer. At worst, you will have to remove the sway bar to pull the balancer if you had to. It is main and rod bearing insurance.

18psi

iTrader: (76)

You sound like you know your way around a track and have more skill than the average track guys here so by all means shoot for 350whp.
Just take lots of pics and videos along the way