O.S. CV-R extra compression

[kwong2001]

Okay, i don't know all the technical terms, but i'm gonna describe what i did.

I took the head off of the CV-R and took the thing metal ring that's in between the head and the sleeve. Basically trying to raise the compression. I ran the car, but the idle seemed a little low.

What kind of effects will this be to my engine? Is it healthy? Will it be positive or negative.

Also, after i broke in the engine (this was a year ago)...the car would do peel outs on dry pavement, now it won't. What gives? Is it time for a rebuild?

 

[NCNitro]

The OS engines only use one head gasket/shim unlike the TRX which uses three. With no gasket in there if there are any imperfections at all in either the head or block you will get air leaks if you do not have that gasket in. I really don't recommend doing this as it can cause running and tuning problems. As far as doing peelouts you might need a rebuild, you might need to tune it better for the current conditions, temp, humidity, etc. to get it to run like it did. How much fuel have you run through it?

 

[kwong2001]

i've ran about probably a gallon to a gallon and a half

 

[NCNitro]

You should get more than that out of it unless it was run excessively lean.

 

[kwong2001]

Hmmm..maybe i should re-tune it. Come to think of it, it probably is running a bit lean. Plenty of smoke comes out on low rpm, but you don't see any in high rpm.

I don't think I need to rebuild it though. It still has plenty of compression, it just doesn't seem to run the way it did new.

 

[mjime714]

If you take out a shim, you should go down in nitro content. If you are running 20%, go down to 18%. and vise versa. If you go up in nitro content, you should add a shim. The higher nitro content, the stronger combustion and the more area it needs to combust. Make sense? cuz it doesn't to me.

If you take out a shim to increase compression but you do not go down in nitro content, you run the risk of breaking something. Its like putting a fire cracker in a large empty foldgers can. It explodes, but not much happens. Now put that same fire cracker in an empty soda can. You get 1 messed up soda can. If you go from a fire cracker in the foldgers can to an M80, you get 1 messed up foldgers can. You need to find something bigger to accomodate the combustion.

 

[kwong2001]

Oh yeah, here's how I broke in my engine.

I ran a tank through. Then another, then i think evey tank after that, i leaned out the idle just a tiny bit because everytime i ran it, it seemed way too rich and sounded like it was gonna die any moment.

Could that be why it doesn't have the torque it should. Also, i did try to tune my car a little and it seem to make good power. I'll try tomorrow if it's dry. It was getting dark today when I did it and I didn't bother to fill the tank so I was on empty almost.

 

[mad sceintist]

heres a link on the topic of removing head shims

http://www.rcnitro.com/rn/articles/10_lobudget.asp

 

[kwong2001]

So should I retune the engine when I remove a shim?

 

[mjime714]

I retune almost everytime I go out because of outside temp will change the characteristics of your engine. When its colder outside, you could lean it out When its hot, you need to richen it up.

When ever you do something to the engine, or something that effects how the engine runs, you should retune.

 

[kwong2001]

I don't like to retune too often though, cuz i'm not super good at it.

 

[kwong2001]

Well, i have the shim left out now...i have re-tuned the highspeed air/fuel, but i still need a little work on the idle air/fuel, just haven't had any time.

I think i'm better at tuning than i thought, i just didn't really give it a try.

I run my car on the street in front of my house, and about the time where I have to hit the brakes (it's about 200ft away) you can hear the rpm's really climb.

I also need to redo the shift point. Which will definately help out with acceleration.

The car overall is getting pretty good...now I just need to learn suspension

 

[Çh®i§tiªñ]

Be careful with not having a shim at all. As stated, the O.S. typically only has one gasket in between. Not having creates a big potential for an air leak which can make for a rough tune as well as a hot running condition. I never recommend not having at least one.

Just my 2 cents......