JohnnieChimpo

Before you reply with, get it tuned or some sort of flaming, make sure you read and understand exactly what this post is saying not what you think I am trying to say.

Two days ago I installed a CTR intake cam. Before I installed the cam I marked where the distributor was so that starting the engine afterwards would be easier. When I was finished with the cam job I put the dizzy back where it was. When I checked it on the timing light it was off by nearly 12+ degrees advanced something like 27 degrees. So I turned it back to 16-17. I checked the marks after the swap and the gears were perfect. So everything is 100% stock except that my intake cam is now CTR.

A trip down the road reveals a pretty big loss in the low RPM area.

A buddy makes the comment, more air in, you need more air out. So the next night I installed the CTR exhaust cam. Then I installed a set of GE cam gears both set a 0.

I take it for another ride. Still a loss of low RPM power but a pretty nice jump in power around 3000rpm and way up near redline 8000rpm. I'm not sure if it has more power than it did when it was stock or if it just sucks so bad that once it is running good it feels fast.

So now I'm trying to figure out why I lost power down low, from idle to 3500+rpm.

The distributor settings before and after really have me puzzled. I know that the ignition timing before the cams was ok because, 1. I set it and 2. I would have been knocking bad if it was really at 25+.

I honestly don't know where the cam timing was before the cam swap but due to the weird distributor timing I think it may have be retarded a tooth. If one tooth is something like 10.5 degrees that sure would explain it.

The car ran fine before the swap. Plenty of low end and pleny to top end.

I can't imagine that Honda would have cut the dizzy marks on two different cams so far appart.

Do you think that it is plausible that the OEM intake cam was retarded a tooth causing good high end and also causing more overlap which would cause good low end?

Has anyone ever run the intake cam retarded one tooth?

What were the results?

Has anyone ever put CTR cams in a stockish GSR and felt a loss?

If I advance the intake cam to gain bottom end is the CTR cam going to cause a valve to hit the OEM GSR piston?

Let me cover some info in closing.
I checked the cam timing with a straight edge after the cam swap, perfect.
I checked the ignition timing, 17*.
I reset the computer.
I set the valve lash to within spec after the cam swap.
GE cam gears are set to 0,0.
The CTR intake cam alone lost power even on OEM cam gears.
This engine is a stock OBD1 '95 GSR engine, 3" Prelude intake elbow to stock airbox no baffles, CTR header, JDM 2.5" cat, Apexi WS exhaust.
Cams have the correct rings to be CTR and I even measured the lift.

Modified by JohnnieChimpo at 5:40 PM 8/18/2005


Modified by JohnnieChimpo at 5:01 PM 8/19/2005

JohnnieChimpo

27 views and no one has tried this?

What is the most anyone has advanced an intake cam?

asubennett

Well you know the answer that I am going to tell you.

1) The "butt dyno" is decieving. You may have gained power and do not realize it.

2) Adjust them cam gears of yours on the dyno so you know what your changes are actually doing.

3) Degree the cams in. I believe CTR cams are 106LCA intake and 108LCA exhaust.

4) If you want to just play around with it. You would be fine to go 4 degress in either direction with your motor and the cams your using. I would start at +2 intake +2 exhasut see if that helps your low end at all.

JohnnieChimpo

OK here's an update for anyone who cares.

I advanced only the intake +4* and left the exhaust at 0* and reset the spark to 16-15*.

Advancing the intake should have brought the power band down a few RPM.

Leaving the exhaust at 0 and advancing the intake caused more overlap. This would cause more power down low.

The off vtec power is pretty nice. It might even be more than with the GSR cams.
There is a drop off in power around 5000 rpm but from 6000 on up it feels extra strong and it wants to pull past 8000. I've always read those posts about wanting to rev higher and thought why? Now I'm thinking that I should upgrade my springs so I can use that new power up there.

Right now my goal is to get rid of the flat spot around 5k.

I'm going to try getting rid of some overlap by advancing the exhaust cam 1 or 2 degrees.

I'd also like to advance the intake cam more but I'm afraid the valves may hit the pistons.

JohnnieChimpo

Another thing I should point out,

Looking at the GE cam gears it seemed to me that turning the intake cam counter clockwise would advance it but when I unlocked the 4 bolts and twisted it around it seems that I was wrong and turning it clockwise advances it.

This means that my original post was wrong and it would appear that my intake cam may have been retarded from the factory.

I'm baffled now and I'm ready to forget about the distributor timing before and after because with my cam gear advanced the dizzy is even farther from my "before cam swap" mark.

asubennett

Advancing both cams is going to increase overlap. To decrease overlap you would want to advance intake and retard exhasut.

As it sits now your intake valves are opening early and closing early and your exhasut valves are also opening early and closing early. So before your intake valves are all the way closed your opening your exhaust valves as well becasue you advanced that cam. Hence overlap is increased.

Also overlap is better for high rpm power not low.

JohnnieChimpo

I've been wrong before and it turns out I am wrong here to.

The bad news is I was correct the first time and I went in and changed it because of something I read on the H-T site.

I'll give you a link to a motorcycle site that has a pic and better explains DOHC cam setup. This guy is Doug Meyer. I know he is correct without a doubt. If you don't know who he is you're not a Kawasaki man. :-) http://www.muzzys.com/articles/lobe_centers.html

Advancing both cams moves power down but doesn't increase overlap. You've made both things happen earlier.

When thinking about overlap, one thing escapes most people, the exhaust happens first. When talking about overlap, it is the amount of time the exhaust valve is still open while the intake is opening.


For anyone else reading this thread and for my own reference, I'll qoute the other site.

"Advancing the intake and retarding the exhaust increases overlap and should move the power up in the RPM range, usually at the sacrifice of bottom end power"

"Retarding the intake and advancing the exhaust decreases overlap and should result in a wider power band at the sacrifice of some top end power."

"usually it is the intake that is moved to change power characteristics since small changes here seem to have a greater effect."

Something else I'd like to add is that retarding the exhaust cam brings the exhaust valves closer to the pistons and advancing the intake also brings the intake valves closer to the pistons.

JohnnieChimpo

Thinking out loud here,

If my intake is at +4 and my exhaust is at 0 that means I pulled power band down and increased overap which should have pushed it back up some.

I think my next try will be +4 / +4 on both. That should be stock overlap and +ing it will bring the band down a few RPM.


As for the *** dyno, LOL you're right but right now I don't want to waste money dynoing since I eventually want to go boost.

The calibration on my *** dyno is pretty good. I drive a 25,500 lb. GVW truck all day. It only has 190hp so it is hella slow. Trust me I can tell when my gas tank is low on fuel.

TrackSpeedRacing

I once ran the CTR cams in my stock JDM GSR motor with the intake cam advanced 2 degrees and the exhaust cam advanced 1 degree. You need to set your ignition timing somewhere between 17-19 degrees btdc. It really depends on your setup but for me these settings seemed to work out pretty well. Good luck

JohnnieChimpo

Thanks dude I'll give that a try.