I'm really starting to regret dropping back down to a 2.0 from a 2.3, and I haven't even turned the new motor over yet . On the plus side, my SCCA rules do allow me to drop out another 90lb from the car for the decreased displacement, but I'm going to miss that spool and response.

 

There are definitely a few decent reasons to go to a 2.4L in SM.

Stripping an EVO to SM limits but not really replacing things ends up right around 2950 on a non-sunroof Evo. The minimum weight is 2940 with a 2.4L and >275 wide tires. A 295/30/18 or 295/35/17 would probably be about the limit of what you can get under the stock body after a lot of hammering? This gives you a 25.3" tall tire, which I think would probably help with the lower rev limit.

If weight loss is the game then a 275/35/18 or 275/40/17 will give you a 25.5" tall tire to help with the lower rev limit and gets you an extra 200 pounds you can pull from the car, putting you at 2740. Realistically, I think it would be fairly tough to legally make it under this weight on the EVO in SM without spending a lot of money?

 

I think it's tough to get under 2800lb without $$$$ in SM. This season my car was running a 2.3 w/ 2910lb min weight and I had the car right around 2940-2950 without a lot of the big ticket weight reduction parts (still have 1pc rotors, stock passenger seat, etc). Running 285/30/18 BFGs and an 8k limiter, I was still able to hit 66-67 in 2nd. I think the ticket would be to go 2.4LR, so that you wouldn't loose much in the rpm range, if any, over a 2.0.

 

Its posts like this that make me want to trade my 2.3 block for a 2.4lr if I had the cash.. Nice tq numbers per lb of boost

 

Just some numbers based on peak piston forces.

On 150mm rods and equal weight pistons:
88mm @ 9500RPM is roughly the same as 100mm @ 8800 RPM.

Add a 162mm rod to the 88mm crank (4G64 block) and it only buys you 100RPM for the same forces.

Add a 156mm rod to the 100mm crank and it gets you 50RPM.

Rod ratio matters very little on rpm capability once you are above about 1.5:1.

It does help with skirt loads and a longer rod with a shorter piston can make an overall lighter rotating assembly. Lower side loads also means a smaller skirt can be used, further reducing piston weight. Overall, rod ratio (as a raw number by itself) isn't very important with regards to mechanical forces on the piston and rod though.

 

Good teaching, right here, my friend.

 

Wow that's a really good read there.

 

Plugging in actual piston weights from Manley gets pretty interesting actually.

The lightest piston is the 25.7mm compression height on the 85mm bore and 17cc dish and weighs 277g. Same piston but in 87mm bore I would estimate to weigh about 20g more.

Comparing a 153mm rod with 100mm stroke in the 4G63 to a 159mm rod and 100mm stroke in the 4G64 block. The lighter piston is much more important in the forces seen by the rod then the importance of rod ratio. The 2.3L should actually be able to rev higher.

This is of course based only on force differences. How the rod ratio affects piston side load, ve, and jerk (similar to an impact load) is a different story though. Just thought it was worth mentioning since so many people seem to think rod ratio is so important on rpm capability.

 

Preach on, brother! This stuff is a lot more interesting than "what kinda eBay brand oil cap should I get?"

 

So you are saying a long rod build cost is not worth it compared to a standard rod build ?

 

What bearing/ring/p2w clearances do you guys run on let's say a motor that is being built to make 800-900 awhp with supporting mods etc.
thanks

 

OK, so for the uninitiated, are you guys talking about boring out the Evo 8/9 motor? Or dropping in a larger engine from another Mitsubishi car?

 

Entirely dependent on what you want the final displacement to be. The cylinder walls should not be overbored more than .040 due to affecting structural integrity of the block. This is especially true of the 64 blocks.

4g63 based strokers -
2.2L - 94mm crank, 153mm rods, custom pistons
2.3L - 100mm crank, 150mm rods, stroker pistons (this motor is probably the most commonly built stroker EVER. Been common for 15 years.)

4g64 based strokers -
2.1 - 88mm crank, numerous rod lengths, numerous piston types
2.2 - 94mm crank, numerous rod lengths, numerous piston types
2.4 - 100mm crank, 150mm/156mm rod, stroker pistons/standard pistons

This isn't by any means a complete list, but is a pretty good starting point for you.

 

A built 2.0lr vs a 2.1 destroker using 88mm oem crank what are rev differences?

I know the benefit to lr 2.0 is thicker cylinder walls and the benefits to the 2.1 destroker is .1 more liter of displacement.

What would you choose for drag car? 40psi+ 700whp+

 

i cant answer that from experience, but if i were gonna go through the trouble of using a 2.4, why not get the full effect and utilize all 2.4 liters?