efr 6258, a good low boost option?
 

After crunching numbers in regards to na vs. Fi, i think I am going to go turbo. Someofit. I autocross 10-15 events a year, and am ready for more power. The boost lag on the turbo cars I have driven made me never want one for auto cross, but I was thinking medium compression(9.5:1?) And low boost.
I have a friend who has moved on from the efr 6258, and is pushing me to use it. My questions are:

1. Is this too big to be useful in autocross?
2. My power goal is 200-220, is this a reasonable turbo for the goal?
3. Is medium compression and mild boost just lame, for any purpose?

My car- 1995 1.8, megasquirt 2, engine rebuild in progress (pending turbo selection)

Thanks,
Ryan

If autocross is your only game, I'd recommend a supercharger. The slow top speeds and the constant off - on throttle in the turns would mean you are mostly out of the range to spool a turbo unless you get a small one. The EFR spools great, but you would be too low in the RPM range to get the most out of it.

Also it would be a waste of an EFR, and even on spring pressure it would likely make well over 200.

I would still recommend going turbo though :party:

Yes.

So you go from 101 ft/lbs to 105 ft/lbs off boost just to inadvertently limit the spark curve you can run up high? It doesn't leave you in a better place. Get a copy of Desktop Dyno software and run the compression differences to see what they give you on a BP's bore and stroke. It is negligible difference in reality. In a NA race engine where you need every 3 to 5 hp on the top end it matters a lot to run a 12 to 1 versus a 8.6 to 1. It matters much more than a 8.6 to 9.5 bump on a turbo car.

I didn't explain that well.

Worst waste of an EFR ever.

You want a broken motor? The EFR is how you get a broken stock motor. It's a mega waste unless you get a built motor, run ALLOFIT, and go in SSM.

It's one of those things that can certainly be done but the result doesn't make you very happy.


Like this:

https://www.miataturbo.net/attachmen...ine=1412716562

:laugh:

I have nothing really useful to add here. but lulz.

Dang it, I was hoping you guys were going to tell me that this was the best turbo for my application ever. This doesn't seem to be the case though. I guess I need to go back to the drawing board. I would like to say with stock rods and replacement pistons for the rebuild. Is this just ridiculous to you then consider putting a turbo on with the stock internals?or was I just trying to put the wrong turbo on this engine?I just don't have the 2000 to drop on engine internals and 3 or 4 thousand to put down for the turbo setup. It's kind of one or the other at this piont.

If you don't have the $3-4k to put down on a turbo setup, then you can't afford an EFR.

Nothing wrong with putting a turbo on a stock motor.

If you're going to pull the engine down and you think you might run some boost someday, seems like a no brainer to throw some rods in it.

A better turbo for your application would be a 2554 IMO.

I'm not sure if you're trying to do the stupidest ting known to miata's, but you're succeeding.

you want a fast spooling turbo that will be easy on the rods get a 2554 or something in that size range price range and run it on stock long block at under 10psi. should meet pretty much all yours goals.

also LOL @ not having money for rods but considering EFR

my plan up until the other night when the turbo was offered to me,was the popular 949 recipe,. 99 head,square top, 4.37. Maybe for the autocross this is still the best option?wait a minute I forgot somebody suggested a supercharger, but they get hated on so hard around here!

General hatered is different from specific hatered. For your specific goals and situation a supercharger would not be completely out of the question.

EFR was only because it's being used as a paperweight in my friend's office.

Then buy it from your friend for cheapsies. Turn around and sell it to someone here. Use the money to buy a 2554 and a clutch and some tires.

You'll spend more on the manifold for the EFR than a used 2554 + log manifold that won't bend your rods.


4.37 (what is this?) rear end sounds positively hideous for autocross.

For your goals, MP62, the smallest garrett BB turbo, or FoST takeoff turbo.
Said by the guy making like 260hp with an EFR 6758.

I just got my 949 twin disc organic in the mail, and the 15 by 9 949wheels should be here next week. But I see where you're going with this. So who needs a EFR for a decent price?

sorry I meant 430 but it's pretty common for the autocross low horsepower guys I think.