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For those considering the CheaTR cam

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Old 08-02-2005, 08:10 PM
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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.
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?
Old 08-02-2005, 10:01 PM
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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?
it isnt the cam, its valve float silly, the cheaTR as a power bands up to 6800 RPM, and hes losing power at 5600, that 1200 RPM could be 25HP, after he gets the dual springs he will prob take off another .2-.3 seconds off his ET

PS- before the cam he was probably running mid 12's
Old 08-02-2005, 11:03 PM
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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
Old 08-03-2005, 12:11 PM
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Originally Posted by greatskiiiier
so a 17.9* and 0.132" increase on the intake is giving you better gas mileage, THATS AWSOME!
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.
Old 08-03-2005, 12:24 PM
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Did you test preload? What length pushrods are you running? Sounds like a pushrod or a spring problem causing valve control issues.
Old 08-03-2005, 01:23 PM
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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.
Old 08-03-2005, 01:41 PM
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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.

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.
Old 08-03-2005, 02:18 PM
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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
Old 08-03-2005, 02:54 PM
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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.
Old 08-03-2005, 05:19 PM
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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.

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.
Old 08-04-2005, 03:56 AM
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Thanks for the info. I know about shimming springs but I was under the imression it wasn't done with Beehives.
Thanks Geof.
Old 08-04-2005, 08:03 AM
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holy ****, nm, i have hardened push rods, when i said stock, i ment lenght. im sorry for the confusion. I got them when i bought the cam.
Old 08-04-2005, 08:07 AM
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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.
Old 08-04-2005, 01:24 PM
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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?
It has a lot of exhaust duration even on a 116 you will hear it with a good exhaust.

Mike
Old 08-04-2005, 02:14 PM
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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.
well if you think about it, it makes sense anyway.the cam is made to add the right amount of air/fuel to the combustion chamber. and the duration and such coupled with the lsa is letting that mixture burn more completely than the stock cam. this has been josh's over analysis hour, please join us next time.
Old 08-04-2005, 02:16 PM
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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
hmm with such and lsa/duration. think itd be good for FI?
Old 08-04-2005, 02:23 PM
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Originally Posted by 8KickassRS9
hmm with such and lsa/duration. think itd be good for FI?
Of course, this cam was patterned after the stock one.
Old 08-04-2005, 02:38 PM
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Originally Posted by PREDATOR-Z
Of course, this cam was patterned after the stock one.
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.
Old 08-04-2005, 02:46 PM
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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.
I do not see why?
LSA on Z06 cam is also wide and have you ever ridden in a SC Z06, wooow.
Old 08-10-2005, 08:47 PM
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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.
I have an Old Man Cam and when I called you guys recomended the 918's and now it sounds like i can "get by" with them and no one said anything about shimming them. I dont have the cam in yet should I sell them and get something else?


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