1776 Engle 120 - High Compression - How Much Boost?

[FrankB]

Hey Guys,

Was just wondering if anyone is running an Engle 120 with a 8.75-9:1 compression ratio and how much boost are you running?

I an in the process of building a 1776 with a CW crank, Mahle 90.5 P&Cs, Engle 120 cam, Dual valve springs, 1.25 ratio rockers and mildly ported stock valve heads. I'd really like to spin it out to 6500rpm if it'll keep making power.

I was previously running 8-10 psi on a stock 1600 with a little turbo (td03-8g), but not sure how the new motor will like it with that high of compression.

Here's a dyno video from my 1600.

https://youtu.be/NTjxeZ2zE_w

[buguy]

Really hard to tell. Intercooler and water/meth would probably help a lot.

[FrankB]

Do not want to run an intercooler or injection set up. Car is super simple and I'd like to keep it that way. Fuel will be 93 octane. Ignition provided by a 009 limited to 23 degrees.

[buguy]

Probably going to be stuck at that 8-10psi then.

[FrankB]

I'm happy with that range. Any ideas of what a high compression 1776 engle 120 motor would make on 8 psi? Car made 105 to the tires on 8 psi on the stock 1600.

[buguy]

A guess??? 130 maybe?
Plug your old numbers into this and adjust to get your 105, then change the displacement to the 1776 and see what it comes up with!
https://www.rbracing-rsr.com/calcboost.html

[Chip Birks]

Hey Guys,

Was just wondering if anyone is running an Engle 120 with a 8.75-9:1 compression ratio and how much boost are you running?

I an in the process of building a 1776 with a CW crank, Mahle 90.5 P&Cs, Engle 120 cam, Dual valve springs, 1.25 ratio rockers and mildly ported stock valve heads. I'd really like to spin it out to 6500rpm if it'll keep making power.

I was previously running 8-10 psi on a stock 1600 with a little turbo (td03-8g), but not sure how the new motor will like it with that high of compression.

Here's a dyno video from my 1600.

https://youtu.be/NTjxeZ2zE_w

If you are building the engine right now, why wouldn't you shim it out a little more to drop that compression down a hair? Seems a little high to me if you are planning on cheap fuel AND boost. Your stock 1600 had less than 8:1 compression if I remember right.

[buguy]

I think my 1600 was like 7.3:1 or something around there.

[John S.]

I agree, shim it out some. You maybe super tight and room for an acceptable deck height and lower your c/r some. Or just change the heads. Better to do it now than always having the high c/r to deal with. The cam will work good enough.

[madmike]

when I had a w120 I've ran up to 15 lbs. with race fuel

[FrankB]

Hey Guys,

Was just wondering if anyone is running an Engle 120 with a 8.75-9:1 compression ratio and how much boost are you running?

I an in the process of building a 1776 with a CW crank, Mahle 90.5 P&Cs, Engle 120 cam, Dual valve springs, 1.25 ratio rockers and mildly ported stock valve heads. I'd really like to spin it out to 6500rpm if it'll keep making power.

I was previously running 8-10 psi on a stock 1600 with a little turbo (td03-8g), but not sure how the new motor will like it with that high of compression.

Here's a dyno video from my 1600.

https://youtu.be/NTjxeZ2zE_w

If you are building the engine right now, why wouldn't you shim it out a little more to drop that compression down a hair? Seems a little high to me if you are planning on cheap fuel AND boost. Your stock 1600 had less than 8:1 compression if I remember right.

We had fly cut the heads a bit to bump the compression up. My compression was right around 8:1.

Additionally, it seems that everyone recommends a higher static compression ratio with the W120 (Most say 8.75:1 at a minimum) as it has a decent amount of overlap. This will in-turn change the dynamic compression.

[FrankB]

when I had a w120 I've ran up to 15 lbs. with race fuel

What compression were you running at that time?

[buguy]

I think when most recommend bumping compression to make a cam work better they are talking NA.

[Steve Arndt]

E120 is a lot of cam for stock valve heads on a small engine. I would advise choosing a better modern grind.

[FrankB]

I think when most recommend bumping compression to make a cam work better they are talking NA.

Not necessarily, too little compression with a large overlap cam and the turbo will be working overtime to fill the combustion chamber. This would in turn cause higher charge temps which would make the engine more prone to detention. That's why the dynamic compression is so important. With a higher static compression ratio, you are using that extra compression to fill the combustion chamber during overlap.

I have always been taught to get away with a much compression as possible so long as it doesn't detonate. This is within reason of course.

Think about it this way, low compression with large overlap is like a professional marathon runner running a race is wooden clogs