Lowered Compression

[Whizzbang]

What exactly is the benefit of lowering compression? What is the lowest you can go? I know that really low compression trucks have to be started with ether but didn't know all the benefits and/or risks(if any) of lowering compression? Thanks

 

[BigB82789]

More room for more fuel and air.

 

[JFlagg]

I believe there is also a slight drop in drive pressures also... but I think its done just to get more air and fuel in the cylinder mainly.

 

[zstroken]

I believe there is also a slight drop in drive pressures also... but I think its done just to get more air and fuel in the cylinder mainly.

I think you mean cylinder pressure.

 

[hpprose]

Lower Compression means less stress on the internal components. Realize that when people are lowering their compression, they are adding more fuel and more air. This means, more pressure when they ignite. Lowering the compression will help from preventing head gasket failure and does reduce EGT’s (only slightly but when you add more air and fuel, you counter that).

How much lower can you go, well depends on what you want to do. 14 to 1 on a dodge, seems to start ok and work on. Lower than that, and you will probably need some Ether. On a Ford a Duramax, I don't have a clue. I know a few fords running 15 to 1 and they start fine, but outside of that, who knows.

 

[JFlagg]

I think you mean cylinder pressure.

Oops, thats what I meant, lol. Good thing you follow me around and check my posts for errors

 

[zstroken]

Oops, thats what I meant, lol. Good thing you follow me around and check my posts for errors

I can't come up with original ideas of my own!

 

[Kman9090]

Well my brother runs 15 to 1 on his 2nd gen and it doesnt like to start under 70 degrees!

 

[zstroken]

12 or 24?

 

[rockjeep73]

15.3 to 1 on my 24valve starts no problem in the cold with the grid heater

 

[BluegrassDiesel]

Well my brother runs 15 to 1 on his 2nd gen and it doesnt like to start under 70 degrees!

What kind of timing?

 

[DieselDiva]

We are running 14.5 in Black Ice. The damn thing was a beast to start no matter what the temp was until we got this new cam in it. Now it only needs a little sniff of ether sometimes as long as it's about 70 degrees.

 

[zstroken]

Hogues Cam?

 

[Kman9090]

24v and i dont think its got the grid heater, and its got a pretty hot cam!

 

[zstroken]

24v and i dont think its got the grid heater, and its got a pretty hot cam!

Dropped the compression on a VP truck? Particular reason why? Planning on Ppumping it?

 

[Kman9090]

Yes it was a vp converted to p pump with a big cam now it's back to a vp truck. grid heaters aren't hooked up so it has a little trouble starting. it didn't want to start today! It doesn't hurt it to lower the compression on a vp does it?

 

[zstroken]

No just not really needed.

 

[Kman9090]

yeah it had a big p pump on it last year but decided to drop it back a notch so you can drive it on the street every now and then. It's not lowered to crazy much just enough for the cam. my CR has the pistons fly cut. I was gonna go with a big cam but went with the street cam instead mine aren't vut that much though very little. Runs lower egts though.

 

[durbin]

so how low before it really starts puffin the white smoke at idle or is alot of that in the pump and such?

 

[roachie]

My truck has stock 16.3 or .7. It will huff the white when its below 40 and cold. Has a constant haze right now. I think timing causes most of it, lower compression does it too.