4.0L RV8 rpm

Kev · Post by **Kev** » Tue Apr 10, 2007 8:10 am

what's a safe high rpm limit for a standard serpentine/Gems 4.0L bottom end. I'm running a Piper 285 with stage 3 heads and it still wants to run at 6000rpm. Can I safely go higher?
Kev

ihatesissycars · Post by **ihatesissycars** » Tue Apr 10, 2007 8:15 am

V8 Dev suggested 6500 for my 4.6 bottom end. The 4.0 should in theory be atleast safe to that also but i wouldn't go any higher unless you can find someone who regulary does on the same components that you have.

On a side note Kev, are you using a ms efi setup with coilpacks?

Kev · Post by **Kev** » Tue Apr 10, 2007 2:26 pm

ihatesissycars wrote:V8 Dev suggested 6500 for my 4.6 bottom end. The 4.0 should in theory be atleast safe to that also but i wouldn't go any higher unless you can find someone who regulary does on the same components that you have.

On a side note Kev, are you using a ms efi setup with coilpacks?

Thanks, 6500 it is then.

Yes I've mounted a 60-2 tooth wheel behind the crank pulley and use the 4 coil lost spark on MSnS. It works well.

Kev

ihatesissycars · Post by **ihatesissycars** » Tue Apr 10, 2007 2:31 pm

Ahhhhhhhhh

did you fancy perhaps letting me pinch a copy of your msq to use in my new setup by any chance?

Kev · Post by **Kev** » Tue Apr 10, 2007 3:37 pm

ihatesissycars wrote:Ahhhhhhhhh did you fancy perhaps letting me pinch a copy of your msq to use in my new setup by any chance?

Let me have your email address and I'll send it to you.

The accel enrichment isn't quite right yet, and don't forget you can't use the trigger settings as they are particular to your setup, but the spark map should be a good start for you and maybe the ve table should give you an idea of the shape of the fuelling curve.

Kev

ihatesissycars · Post by **ihatesissycars** » Tue Apr 10, 2007 3:51 pm

Wow you're a star! My email addy is baldingnorton at hotmail dot com

What size injectors are you using? I'm going to start of with some standard hotwire jobbies to make life a bit simpler rather than the 33lb ones i have.

Kev · Post by **Kev** » Tue Apr 10, 2007 4:19 pm

standard green injectors; they go to 82% open at full throttle, so I guess they're not far off maxed out, but they will take a bit more fuel pressure so I'll be keeping them for a while yet.

Kev

email sent

ihatesissycars · Post by **ihatesissycars** » Tue Apr 10, 2007 4:59 pm

Thanks Kev! If you've the same injectors as me then i'm hoping your msq should be fairly close to mine as our engines are very similar.

Good luck with yours!

Gav

Kev · Post by **Kev** » Tue Apr 10, 2007 5:23 pm

for the first start I would add around 15% fuelling to the ve table as it's dead easy to tune the table once you can run the car, and your engine will be different. 2 hours should see the fuelling just about spot on when you can run it on the road.
You can use the scalar in megatune to up the fuelling by 15% across the board.

Disable the closed loop running in the msq while you tune the VE table.

My AFR table should be close, I haven't tried changing the required AFR at full throttle yet, that's the next job to fine tune.

BTW all this assumes you have a wide band lambda, if you haven't then get one, it's the best tuning aid ever invented, bar none.

Kev