Jump to content

3.5 supercharger from flap to squirt


Random_badger

Recommended Posts

After significant time away from playing with megasquirt (it's all been working fine, thanks to all on here, no pinking popping or vac advance problems) I've now purchased a 3.5 v8 with a sprintex supercharger  currently fitted with a flapper system.  The engine is a known runner, and cam from and overfinch fettled RRC.  Various internal components are unknown parts, it was built by a known drag race engine builder and I am currently looking into the history to find what has been done.

Aside from my wifes disappointment with me for grinning like a school boy when I told her, how much difference will there be in the fuel and ignition maps when I have the squirt fitted?

Are there any additional componentry to fit?

Will the standard hotwire injectors and EFI pump support the fueling requirements?

Hoping to fit over the summer trialling season break but want to be as prepared as possible before hand to avoid too much head scratching.

Link to comment
Share on other sites

And very deep pockets :P

I know a guy who knows a guy who had one... 6-8mpg(!)

Biggest difference in fuel and spark maps will be that the left hand side will go up to (around) 150 mpa, as you now have a boosted situation. Do you know what sort of PSI you will be running? I assumed low as only a RV8 :) Think most MS boxes come with a 2 bar MAP sensor, so you are good to 14psi with that.

As for fuel and spark.... well the more important one is spark, as I am sure you are aware, once you get above 100mpa you will need to retard the spark further to prevent knock. Do you know how it is done currently, or is it a horrible lashup with a dizzy? (as I suspect!)

Once you have spark eyeballed in you can then autotune the fuel, with a sensible FPR table and a wideband, and you'll be golden, in theory.

As for what else you will need.... hmmm, well I reckon unless you are going silly with boost, your hotwire injectors will likely be OK, given it is 'only' a 3.5l, which was 155BHP as best in a LR, and the 3.9/4.2 was a fair old chunk more (190-195BHP), and there is some headroom in them at that power level for sure. I've not dynoed my played with 4.0l but suspect that is around 220-230BHP, and that is on stock hotwire injectors.

Fuel pump -yes, the early flapper type fuel pump will be fine, it pushes a good amount of fuel, and is what I use.

 

 

 

Link to comment
Share on other sites

True, whoops :)

That's 21psi of *boost*,  28psi absolute, so 1.5BAR boost, 2.5 absolute.

Doubt you will *ever* get that far, think the sprintex ran about 6psi, now I think about it.

And forgive my stupidness above, should be kpa, not mpa, seems I infected Fridge at the same time!

Link to comment
Share on other sites

Knew it was one or tother, MPX250 is the part number, bit of a giveaway ;)

If the original supercharged lump ran stock pump & injectors then no reason you can't. Lazy option is get it set up with sensible boost, start tuning gently (as you should anyway) and gradually ramp up - if the injectors ever get over 80% duty cycle, you need bigger ones.

Link to comment
Share on other sites

Not too worried about fuel, as it is only used for trialling once a month, doing it to see if I can  :) 

Thanks for the responses.  Found a bit more info, it's a DPR/sprintex charger conversion by DPR/Mr Six.  Again still don't know what the internals have had done to them, if anything.  The motor in the trialler is currently a 3.9 with MS, the plan will be to swap the MS onto the new engine, including the 3.9 Hotwire injectors, fuel rail, etc etc.(I've had problems with flapper resistor packs previously).  So good to know the standard injector/pump set up will work.

Haven't seen the engine yet (but too good a deal to turn down) but it includes an auto box and Tx box.

I am most concerned about the spark issue and think i'll have to do some research to find a sensible mild base map, currently the 3.9 is as aggressive as I think you can go with a standard engine, can't hear any pre ignition, but at full bore with the exhaust outlet under my bum I can barely hear  myself think! 

Thankfully the 2.5 bar sensor should be ok, but having read the thread listed will need to look a brakes, unless the engine has the bits needed (or could I move the Vac tubes to the inlet side of the blower?)

Are there any other people running this type of set up who'd be prepared to send over a safe(ish) base map/tune?

From most comments the standard MS can handle the levels of boost that I'll be looking at.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...

Important Information

We use cookies to ensure you get the best experience. By using our website you agree to our Cookie Policy