For those considering the CheaTR cam
Originally Posted by black_ws6
Hmmm. I lost almost 3MPH going from a TR220 cam to a 231/237 cam + 918's and my ET is about the same. I am curious to see what happens when you throw in the duals.
Originally Posted by TroubledWine3
I know somebody with a mild bolt-on A4 WS6 with the 231/237 cam that runs consistent 12.2s. Maybe your problem isn't just the cam?
PS- before the cam he was probably running mid 12's
when setting springs. you should first determind a safe margin. then test each spring and set them according to pressure within the safe margin. reason being is the springs vary in height and pressure from the manufactor.the motor will run out much smoother having equal pressures, rather than equal heights.
matt
matt
Originally Posted by greatskiiiier
so a 17.9* and 0.132" increase on the intake is giving you better gas mileage, THATS AWSOME! 
I am breaking in a clutch too, that could also be a part of it, easy driving, but in all honesty, i did get better then average miles last tank. stock Push Rods, 918's with very low miles. My Dual's are here, have to work tonight though...sigh, will have them on though and ready for saturday night.
Ill let you all know as soon as i know something.
Ill let you all know as soon as i know something.
Originally Posted by Scoobie
stock Push Rods, 918's with very low miles. My Dual's are here, have to work tonight though...sigh, will have them on though and ready for saturday night.
Ill let you all know as soon as i know something.
Ill let you all know as soon as i know something.
I have found better results going with a hardened pushrod. If the springs don't fix your problem look at the pushrod. It may be flexing.
For the record we have turned that intake lobe pretty high in the past with the 918 springs. I am not saying the springs aren't causing it (if they aren't shimmed properly) but IMHO the stock pushrods should definitely looked at carefully.
I agree with Geoff about the pushrods. We all think that reducing the weight on the valvetrain is going to make more power, well your correct, as long as the weight reduction does not affect the integrity of the part. Pushrod deflection has been studied greatly in the last few years and it has been found that light weight small diameter pushrods are not the answer. Matter of fact quite the opposite. Heavy wall large diameter pushrods don't deflect and because of this make more power and negate the idea that "lightweight" is the answer.
Chris
Chris
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TECH Senior Member
Joined: Mar 2004
Posts: 14,620
Likes: 17
From: BFE
Umm question: Since when did we start shimming 918's??
And it has been discussed before that TR lobes are between XE and XE-R so how do you explain 918's handling .612 lift XE-R and not a TR lobe (without shimming)
From what I know (I could be wrong) but Beehive springs should not be shimmed for harmonic purposes.
Scoobie, you never mentionned stock PR with that cam. Of course they are flexing, I'm even willing to bet that some are bent.
And it has been discussed before that TR lobes are between XE and XE-R so how do you explain 918's handling .612 lift XE-R and not a TR lobe (without shimming)
From what I know (I could be wrong) but Beehive springs should not be shimmed for harmonic purposes.
Scoobie, you never mentionned stock PR with that cam. Of course they are flexing, I'm even willing to bet that some are bent.
Originally Posted by PREDATOR-Z
Umm question: Since when did we start shimming 918's??
And it has been discussed before that TR lobes are between XE and XE-R so how do you explain 918's handling .612 lift XE-R and not a TR lobe (without shimming)
From what I know (I could be wrong) but Beehive springs should not be shimmed for harmonic purposes.
Scoobie, you never mentionned stock PR with that cam. Of course they are flexing, I'm even willing to bet that some are bent.
And it has been discussed before that TR lobes are between XE and XE-R so how do you explain 918's handling .612 lift XE-R and not a TR lobe (without shimming)
From what I know (I could be wrong) but Beehive springs should not be shimmed for harmonic purposes.
Scoobie, you never mentionned stock PR with that cam. Of course they are flexing, I'm even willing to bet that some are bent.
We ALWAYS shim any spring we run to somewhere between .050" to .100'' from coil bind. Any quality spring can be run in this manner without a problem. The reason for this is that if the spring is too far from coil bind you will get what is called 'spring surge'. Essentially the spring can't properly control the valvetrain harmonics once the acceleration goes beyond a certain rate and shimming the spring relatively close to coil bind gives you more lattitude in this area. This practice has been fairly common in a lot of forms of professional racing for a while now.
The acceleration rate of the XE-R and the TR lobes are very similar: Since the TR lobe has less lift we need to actually shim it more to get the same open height.
Also, about shimming the spring, this was never mentioned to me before, and ran a TR224/224 112 for 19K miles or so without any problems. I also spend a good hour of every day on this website. Never read that. Installed them as they are, out of the box. Maybe this issue should be mentioned on the website geoff, so its not just assumed. I dont put blame on anyone, i ran a .600 spring with a .600 cam, but i will be suggestiong dual springs to anyone on this website who want to run this camshaft.
Originally Posted by FUN LS1
I was guessing you were right at the .600 lift limit for 918s, but I thought the CheaTR cam had a.610 IL. Custom grind? Why the lope at 117 LSA & relative low duration on the intake??? What's the overlap?
Mike
Originally Posted by Scoobie
maybe it's because i cant get it up to 6K I am breaking in a clutch too, that could also be a part of it, easy driving, but in all honesty, i did get better then average miles last tank.
I am breaking in a clutch too, that could also be a part of it, easy driving, but in all honesty, i did get better then average miles last tank.
Originally Posted by V6 Bird
It has a lot of exhaust duration even on a 116 you will hear it with a good exhaust.
Mike
Mike
Originally Posted by PREDATOR-Z
Of course, this cam was patterned after the stock one.
TECH Senior Member
Joined: Mar 2004
Posts: 14,620
Likes: 17
From: BFE
Originally Posted by 8KickassRS9
well with that much of an lsa, overlap seems to be an issue. but i guess since the duration is relatively low i can why itd be decent.
LSA on Z06 cam is also wide and have you ever ridden in a SC Z06, wooow.
Originally Posted by Geoff
We ALWAYS shim any spring we run to somewhere between .050" to .100'' from coil bind. Any quality spring can be run in this manner without a problem. The reason for this is that if the spring is too far from coil bind you will get what is called 'spring surge'. Essentially the spring can't properly control the valvetrain harmonics once the acceleration goes beyond a certain rate and shimming the spring relatively close to coil bind gives you more lattitude in this area. This practice has been fairly common in a lot of forms of professional racing for a while now.
The acceleration rate of the XE-R and the TR lobes are very similar: Since the TR lobe has less lift we need to actually shim it more to get the same open height.
The acceleration rate of the XE-R and the TR lobes are very similar: Since the TR lobe has less lift we need to actually shim it more to get the same open height.