boost vs fuel nytro/apex

[Tuesday]

Why is it that a apex with a head shim can only run 12lbs boost and a nytro with head shim can run 15lbs boost on premium?

I am told the mcx kit on the nytro with head shim and timing at lower alt will pull 12-13 lbs boost and as you increase in alt it will automatically increase the boost to 14-15lbs and can be accomplished with a decent prem fuel.

Been lurking alot on the t-4s but now that I have me own I have a few questions.

Later

PS. Regardless I just picked up 20 gallons of AV gas to be safe.

 

[Tuesday]

anyone?

 

[julio]

?

a friend of mine runs a mcx on an apex with shim. it runs 15 lbs at elevation with pump prem. but if you are running a different kit I would think it has to do with heat of the charge air. they also say the apex needs better fuel, may be due to the rpm it turns compared to the three holer.. just my thought.... julio

 

[TBird]

I assume you talk about MCX in both Nytro and Apex!
In the beginning MCX released their kit with 12lbs, because they wanted a bulletproof kit that would withstand much abuse, bad fuel and long pulls, now they have had many years under the belt with their kit and learned that they was "to conservative" and rised the boost on Apex, if you add the extra fuelpump, this goes for the Nytro also.

Experiance says that Nyto might withstand a little more boost then Apex because of better head design, thanks to 4 valve the valves are bigger and cools better, Apex on the other hand has higher rpm which is a good thing, i hope next Apex has 4 valves and even higher rpm then todays Apex = can withstand very high boost levels.

 

[JSCC]

The added compression makes detonation happen easier. So you cannot cram as much air (boost) into the cylinders with the same quality fuel.
The good thing with the added compression is first, you don't need to run as much boost as you would with less compression, as the compression itself compounds the boost making more power.
And second, the added compression helps the bottom end power and response much better. If you ride at high altitudes it becomes much more prevalent.
However, if you want to run a ton of power through the engine, dropping compression is a cheap way of allowing yourself to gain more power on the top (higher boost).
If you ran high boost on a stock block, it would start to expand the cylinders at the top and in essence, ruin your block. The only way around that is to have a block made with bridged cylinders. This I doubt would be cheap.
So to sum it up in my humble opinion. If you want to run big boost, you need to drop compression. But if you stay with a mild boost amount, and don't mind buying a little better fuel, you will be happy with the bottom end response, and overall power stock compression gives you.

Hope that helps...

 

[Tuesday]

I assume you talk about MCX in both Nytro and Apex!
In the beginning MCX released their kit with 12lbs, because they wanted a bulletproof kit that would withstand much abuse, bad fuel and long pulls, now they have had many years under the belt with their kit and learned that they was "to conservative" and rised the boost on Apex, if you add the extra fuelpump, this goes for the Nytro also.

Experiance says that Nyto might withstand a little more boost then Apex because of better head design, thanks to 4 valve the valves are bigger and cools better, Apex on the other hand has higher rpm which is a good thing, i hope next Apex has 4 valves and even higher rpm then todays Apex = can withstand very high boost levels.

This is what I was thinking.

Thanks T-Bird

 

[Tuesday]

The added compression makes detonation happen easier. So you cannot cram as much air (boost) into the cylinders with the same quality fuel.
The good thing with the added compression is first, you don't need to run as much boost as you would with less compression, as the compression itself compounds the boost making more power.
And second, the added compression helps the bottom end power and response much better. If you ride at high altitudes it becomes much more prevalent.
However, if you want to run a ton of power through the engine, dropping compression is a cheap way of allowing yourself to gain more power on the top (higher boost).
If you ran high boost on a stock block, it would start to expand the cylinders at the top and in essence, ruin your block. The only way around that is to have a block made with bridged cylinders. This I doubt would be cheap.
So to sum it up in my humble opinion. If you want to run big boost, you need to drop compression. But if you stay with a mild boost amount, and don't mind buying a little better fuel, you will be happy with the bottom end response, and overall power stock compression gives you.

Hope that helps...

I understand this concept but was wondering more about the differences in boost levels between apex/nytro pump gas set ups.

Thanks for the info.

Right now at 15lbs its pulling my arms off!

 

[JSCC]

Ahh, understand.

While I dont ride either with pump gas, I do run both our Nytro and Apex at 12lbs stock compression, on Avgas. 8-10,000'. If that matters....

 

[zebiraross]

Have a buddy here that said with the upgraded fuel pump/programing on the mcx Nytro you can run 17 psi on pump prem. He was told this by Mark Leipheimer who knows a lot about the mcxpress kits. I shook my head at it but aparently Mark has done the homework and knows better then me with that kit. Just what I was told...

 

[TBird]

Have a buddy here that said with the upgraded fuel pump/programing on the mcx Nytro you can run 17 psi on pump prem. He was told this by Mark Leipheimer who knows a lot about the mcxpress kits. I shook my head at it but aparently Mark has done the homework and knows better then me with that kit. Just what I was told...

Yes, i know of many that run 17 psi with their Nytros and 16 psi with Apex on Premium, which i have written in an earlier thread, and this on sealevel....
This seems to work great if you have good Premium, but what happens when / if you get a bit less good fuel? I might be to conservative, but better safe then sorry i think!
I have a high / low switch because i doesn't have self control enough to get of the throttle if i am uncertain of fuel quality, it's easier to switch to low boost setting and keep jamming the funometer (throttle) .

 

[Tuesday]

Yes, i know of many that run 17 psi with their Nytros and 16 psi with Apex on Premium, which i have written in an earlier thread, and this on sealevel....
This seems to work great if you have good Premium, but what happens when / if you get a bit less good fuel? I might be to conservative, but better safe then sorry i think!
I have a high / low switch because i doesn't have self control enough to get of the throttle if i am uncertain of fuel quality, it's easier to switch to low boost setting and keep jamming the funometer (throttle) .

Head shim, cam timing and a few gallons of AV gas should give me peace of mind at 15lbs at altitude.

Thanks for the input.