Come winter - build

[mmt 15]

Dear engine builders, 

This winter I will start my new engine build. As I will be Racing e30 M3’s with a mind blowing 350 hp I need quite some kick to be able to sort of keep up. 

The engine needs to be N/A, 1,9 mi16 head and steel block. 

I allready have the mi head with a decent set of cams / better springs and a steel bottom. I would also like to use the gti6 crank and pistons I also have lying around. Max 2000cc  Per regulations. 

 

How would that work together? Will the mi head work with gti6 pistons and rods? I guess compression ratio is a thing to get right. 

 

I Will be using 45 mm ITBs and programmable ecu.  

 

Hoping to keep the components as stock as possible. 

 

Any ideas or pointers-?- aiming for +250. 

 

Thanks 

 

/M

Edited October 20, 2022 by mmt

[welshpug 1,657]

Wont get much past 200 on stock pistons, nowhere near enough  valve clearance nor compression volume  (dome)

[mmt 15]

Thanks G, what would it take to make above 250? Would it be easier to Tune a gti6 rather than using the mi head? 
been searching the Forum and most builds is above 2.0 L or forced induction. 

[petert 586]

Regardless of the components, you need to spin it past 8000 to make 250hp. To make power past 8000 you need big cams and thus this is where the GTi6 pistons are a severe limitation. The standard pockets are woefully shallow and there's not enough material in the crown to cut them deep enough for the cams you need. Additionally, the rods are a press fit, so you can't even use those with an aftermarket piston.

 

If you want a budget build, I'd use XU10J4 pistons and rods. You can machine the pockets deeper and the rods are full floating. Otherwise, you'll need to buy new rods and pistons.

 

To get the compression as high as possible, deck the block 1mm if using XU10J4 pistons/rods (to obtain zero deck clearance), o-ring the block or head and use a 0.7mm copper gasket. Even this will only get you to 11.2:1 with an Mi16 head. A GTi6 head will get you to 12:1, which is where you need to be.

 

It's also easy to fit decent double springs to the GTi6 head, where as the Mi16 head will cost a lot more; machining guide bosses and making double spring seats.

 

The GTi6 head already has the cam sensor, so you can run full sequential injection and direct fire ignition. The GTi6 head also already has vernier pulleys.

 

It will be easier to make the hp with 48mm TB's.

 

Fit a dry sump to make an easy 15hp and have less stress about oil surge.

 

Have you measured the bore of your current block? It might be worn beyond use for 86.0 pistons anyway.

 

 

 

 

Edited October 22, 2022 by petert

[mmt 15]

Thanks for your extensive answer Peter. Great sharing. 
 

No- I did not meassure the bore yet. 
 

Would you get the gti crank balanced or are they normally ok ready to use? 
 

if the block is decked 1 mm would that mess up valve clearance?  
 

How about injectors- Will the gti6 ones be able to keep up. I’m told they are!? 
 

Found a solid lifter kit for the gti6 from Spooks -any good or is there a short(er) Cut to solid lifters- guess 8000 rpm calls for solid lifters?  And uprated springs???
 

thanks again. 
 

/M

[petert 586]

Injectors, no. You’ll need 400cc approx, for 85% at 3 Bar.

Rebalance everything - crank, balancer (new solid), rods, pistons, flywheel and pressure plate.

Solid lifters are mandatory. Arrow also sell them.

Buy springs to match from Catcams.

Decking is essential to minimise quench distance and increase CR. Once completed, a test fit with new thinner HG will allow you to calculate how much deep the pockets need to be.

 

Lots of good questions and I’m sure you’re aware that it costs a lot more money to spin at 8000 than 7000. Just put a K20A in it and be done. 

 

Edited October 22, 2022 by petert

[welshpug 1,657]

those E30's are 2.5's if they are running that much power, and revving beyond 9k

 

surely if you are competing directly against them you can go 2.2/2.3 ?    you can relatively easily be a lot lighter than an E30, the Group A cars were 940kg.

[petert 586]

I still think you're being tight arsed in regards to the pistons:

 

1. It's unlikely the std bore will be suitable for std pistons. Whilst you can run 0.001-00015 more clearance in a race application, I think you'll find the bores will be toast and bigger than that in places and a precision hone won't clean them up. A hone for a forged piston may however, which typically run 0.002-0.004" more clearance.

2. Most classes of racing allow for an overbore. I'd be surprised if you couldn't run 86.50mm.

3. I'm not even sure the crown of an XU10J4 piston is thick enough to be machined deep enough for the cam profile(s) you need. I'd suggest the inlet pockets need to be at least 5mm deep. You'd need to do some research by cutting open a piston.

Edited October 24, 2022 by petert

[DamirGTI 342]

Can always sleeve the block back to std. bore spec. if specifically wants to use/retain std. piston size ..

 

D

[SRDT 175]

You can probably bore it according to the manufacturer's spec but only as long as you still remain under the 2000cc class limit. If so that is no use on a 1998cc XU10.

 

Regulations seems lax if you can run a 16v engine with a mix and match of head and block from other cars. Do you need to only use PSA engines?

[mmt 15]

On 10/24/2022 at 7:37 AM, petert said:

I still think you're being tight arsed in regards to the pistons:

 

1. It's unlikely the std bore will be suitable for std pistons. Whilst you can run 0.001-00015 more clearance in a race application, I think you'll find the bores will be toast and bigger than that in places and a precision hone won't clean them up. A hone for a forged piston may however, which typically run 0.002-0.004" more clearance.

2. Most classes of racing allow for an overbore. I'd be surprised if you couldn't run 86.50mm.

3. I'm not even sure the crown of an XU10J4 piston is thick enough to be machined deep enough for the cam profile(s) you need. I'd suggest the inlet pockets need to be at least 5mm deep. You'd need to do some research by cutting open a piston.

Thanks again. Read somewhere that the gti6 pistons Can only be machined 1 mm. 
 

it is a combined class I’m in the Max 2L class competing with golf mk 1, Sciroccos, which I outrun on most good days. The M3 boys are my next target. 
 

I need to use only PEugeot(psa) parts. Custom parts is also allowed. 

[welshpug 1,657]

Correct on the +1mm for the gti6/rfs piston  cutout increase, Bridgecraft engineering here in the UK have done a few and have a jig setup to do them.

 

Tbh if you need any more than the +1mm you are likely to benefit from more compression, longer  rod and lighter piston assembly.

 

 

Word  of warning on the aftermarket stuff, some of it is not fit for purpose off the shelf!!

Edited October 26, 2022 by welshpug