head shim or not?

[WesG]

I am looking for real world performance differences between running the head shim and not running it in an apex. LB per lb of boost, throttle response, power output for the fuel ie same fuel in both, cam timing for running without the shim, and other info that is related.

 

[Ted Jannetty]

I am looking for real world performance differences between running the head shim and not running it in an apex. LB per lb of boost, throttle response, power output for the fuel ie same fuel in both, cam timing for running without the shim, and other info that is related.

Cylinder pressure determines HP so if you start with High compression and you add boost the FUEL is the LIMTER OF HP so around 8 psi on 93 octane.

By lowering static compression you can run more boost on 93 octane fuel.
Giving up low boost performance for High boost performance.
Throttle response suffers and so does fuel mileage.

Your still limited by the FUEL, depending on how low you lower the static compression, 10.5:1 can tolerate about 11 psi on 93.
9.5:1 can tolerate 15 psi on 93.

Your giving up compression in exchange for more airflow across the engine and everyone knows an engine is an air pump and the more air you can get through it the more power you can make.

The bottom line is, less compression = less power per lb. of boost especially in the lower boost ranges.

For all practical purposes on an Apex 3 stock head gaskets and 11 psi boost seems to be way more than anyone needs for reliable trail riding and the ocasional blast across a lake.

For conversation purposes my personal RX1 engine is still a Virgin and I run 22 psi boost on Sunoco 118.

 

[mulot30th]

Are you feeling your rx1 engine on 22# of boost (300+hp) is still somewhat reliable?


I wonder how much I could push boost reliably on my apex mtn.... on strait c16.

 

[Ted Jannetty]

Are you feeling your rx1 engine on 22# of boost (300+hp) is still somewhat reliable?


I wonder how much I could push boost reliably on my apex mtn.... on strait c16.

Keep in mind I also have MSD ignition with custom timing curve, and Yes I beleive it is very reliable with this tune up.

The engine already had 4000 miles on it before I turned it into a prostock and I have logged over 500 1/8 mile passes at WOT.

I have not Dynoed it Yet but the Math says 330 HP, Who Knows?

Ted.

 

[powderlites]

Apex head shim

I would check into how much fuel you have for big boost with EFI! as well as octane.
Don't run it lean and Ted can make more power because of custom timming control.

 

[thinksnow]

BOOST

About how much boost can I run with straight AV fuel with the stock motor? I have it at 11-12# now and I am wondering if I can try 15#????

 

[Ted Jannetty]

Re: Apex head shim

I would check into how much fuel you have for big boost with EFI! as well as octane.
Don't run it lean and Ted can make more power because of custom timming control.

I agree we should differenciate between RX models and Apex Models during these discussions.

 

[Ted Jannetty]

Re: BOOST

About how much boost can I run with straight AV fuel with the stock motor? I have it at 11-12# now and I am wondering if I can try 15#????

As long as the tuning is good and the AV fuel is a True 100 octane 12 lb. is max

You need 105 for 15 psi on stock compression.

 

[mulot30th]

Re: Apex head shim

I would check into how much fuel you have for big boost with EFI! as well as octane.
Don't run it lean and Ted can make more power because of custom timming control.

I already made 287hp in 18 psi and strait c16... (way too much octane there).

I chickened out going with more boost because I were thinking stock bottom end would not take it...

I do have wideband AND knock sensor, so I will know when its too much for the fuel.

What timing device I could easily install to retard it proportional to boost?

 

[summitking]

sled

MulotTurbo Ripntear runs 20 + lbs of boost and a 60 shot of ice nitrous on a stock engine with a head shim running straight c 16. Im going to yank my head shim out and go with a timing control box from synergy and run 15 lbs of boost on 100 av. Once you ride a turbo with stock compresion theres no going back to lowered.
Lots of wicked info on this site keep it coming guys i might learn something lol

 

[mulot30th]

I agree on high compression throttle response, its real great!!!!

Low compression is great for supercharged sled though! My rx1 blower has 9-1 pistons in it, and I have seen no decrease in throttle response, instant 12# of boost from 4000rpm to cutoff.


So stock bottom end good for 320-330 reliable hp assuming no knock?

I need it to be reliable since I do not trail ride, only ride in powder in places I could not get out of in case of failure....

 

[MEAT]

I ran my 04 rx1 with no shim between 8 and 12 lbs at 3-6000ft *lbs av gas and 12 lbs with 110 polaris gas ) and it was an animal. That was in 04 now I want to remove the shim and go back to stock compression and lower boost. I have had problems ever since I installed the shim with gasket leaks clutch heat broken header throttle chop boost leaks spun the driver on the shaft under hood heat etc. Yes there is fixes for all that and I have done some of them, but in the back of my head on a big pull I dont trust that absolutely everything is going to hold together as I have had too many close calls in bad places. Just my 02 cents.

 

[summitking]

sled

MEAT so is it your engine you dont trust or the sled?MulotTurbo i would love to see a vid or your rx1 with that SC.Im not a hunderd percent sure but i think Mike irmen and the big alpine guys run a stock bottom end and they are running in the 20s for boost and Nitrous and they havent blown up.

 

[mulot30th]

Here is a video of:
RX1 supercharge that weighted 730# at the time and ran 9# of boost on this video (intake was completely iced up)
vs
172hp twin piped ported M8 that weighted 550#


Rx1 is 153" track while M8 was 162"

http://media.putfile.com/rx1-vs-m8


Here is a short video so you can see the incredible throttle response!!
http://www.youtube.com/watch?v=ZPG7w9yNVjw


On this last video, you can see it, the closest to camera which started after every other machines (including my turbo apex) but quickly got in front of everyone (for like 200 or so feets).
The whine your hear at start of video is the blower.
http://media.putfile.com/Drag-4


But you will not see skis high up in the air... simple... I am no fanatic of skis up in the air, so I set my suspensions accordingly.

 

[summitking]

sled

The throttle response on that thing is wicked . I would like to build a vector with a short track and a sc would be a wicked spring snow sled