2.2E or S pistons in 2.4E
 

Thinking about putting 2.2E or S pistons in 2.4E. Are the cylinders the same (can I use a complete 2.2E or S set of pistons and cylinders)?

The cylinders are the same between the 2.4 and 2.2 engines. The difference is in the crankshaft. Also though if you go with 2.2S pistons you'll end up with a Compression Ratio of about 9.6:1 and with the 2.2E's about 9.0:1. I'm currently building a 2.4E with 2.2E pistons.

Hi Tim,

I know that BA said for some reason the CR comes out to 9.6:1 using 2.2S pistons on a 2.4 motor but it just doesn't add up. If the 2.2S pistons were 9.8:1 on the shorter stroke they can't go down in compression on a longer stroke. They go up. So either Porsche is wrong or Bruce is.

If Porsche is correct in their CR figures on the 2.2 motors then I'll bet you end up with about a CR of 9.6:1 on your car. Not bad.

Bobby,
BA states that porshce ussually overestimated thier CR. I tend to belive that since the euro 3.2's had a CR of 10.3:1 (from the book) but run well on pump gas and yet aren't twin plugged and are over the 10:1 "limit"

Compression on a longer crank can go down if the head volume is larger.

That's why you CC and measure everything up.

Jamie,
The head volume between the 2.2 and 2.4 is exactly the same. The only head that I know of that is different from 2.2-2.9 is the 2.8 RSR had about an extra 10cc's of volume.

I did specifically ask Bruce about this confusing swap (with respect to CR.) I haven't asked Steve just yet - maybe he can chime in?

-Wayne

This has got me wondering as well. I'm building one of Wayne's "Top Engine Picks," a 2.4T with 2.2E P/C's and cams. I've read in Bruce's book that the same motor with 2.2S P/C's has about 9.6:1 compression, where Wayne's book says that my motor will have 10:1 compression. I'm tending to agree with Tim here, thinking that the compression will be less than 9.6:1, but I have a hard time believing it will be as low as 9:1, since that's what the stock 2.2E's had.

Anyone have a more definitive answer? The heads are going on this weekend, and I'd sure hate to find that I need to twin plug it once it's together. I'd rather just run some 2.4E or S pistons to lower the compression a bit. Remember, us Cali guys are stuck with 91 octane max.:(

BTW, I did the deck height check, and I have plenty of clearance there.

Sorry to hijack the post, but I've been wondering about this for weeks now. :confused:

Thanks,
Jim

Jim,
I just looked at my rebuild and I see what you mean. I think that's a typo. I've seen the difference between a 2.2S and a 2.2E piston and there's more dome on the S. So I don't get where he came up with a 2.2E engine with a 70.4mm crank has more compression than a 2.4 engine with 2.2S pistons. In the BA book he mentions that the 2.2-2.7L heads are exactly the same sans the ports and intake (MFI, CIS carbs)
Tim

Tim,

It's good to have someone out there building the same motor as me, most likely with the same thoughts and questions as well. As a matter of fact, I was just out in the garage reading BA's instructions on how to accurately measure the compression ratio; it's something I'll probably try this weekend before installing the heads. If nothing else, it might provide a real world spec for those of us building a 2.4/2.2E piston motor.

I'll try to post results this weekend.

Geeze, this will really take me back to my college chemistry/physics/calculus days, but what the heck, it's good to excercise those brain muscles once in a while, eh?:D

Jim

Jim did you ever measure the compression ratio? I am converting a 2.4T CIS and probably going E pistons (used), cams, and MFI. Did you finish your engine?

Seems to me that if the piston arrives at TDC at the same deck height between the two cranks, you will get a higher CR with the longer stroke with each piston choice.

So, I am only saying that if I replace the crank and rods only in my 2.2S motor with the 2.4, and the deck comes out the same, my 9.8:1 is going to go over the top due to more volume being compressed into the same head. If the deck changes with these crank swaps, then all bets are off. If you don't know your deck, you can't figure your CR, no matter what else you know about head cc, etc.

Is there any reason to believe that the crank/rod ass'y in the two motors, 2.2 an2.4 do NOT go to the same deck?