retarding stock exhaust cam?

1fast97gsx · Jan 1, 2005

I've heard of a few people ( eric @ ams for example ) stating they made 500+ hp on a stock head but they retarded the exhaust cam 1 tooth. How many degrees is 1 tooth equal to and what are the negative effects of doing this? My car will be running stock cams due to emissions and I want to sell the car anyways so why spend another $600 on aftermarket cams .. however I have a set of adustable gears still so I was interested in retarding the exhaust cam and what that would do for me. How would it change driveability off the track and gas mileage? Any input would be helpful.

1fast97gsx · Jan 1, 2005

nevermind ... searching helps http://dsmtuners.com/forums/showthread.php?t=96264&highlight=retarding+exhaust+cam

What do you guys think of a 3-4 degree retard on the exhaust cam?

Sk8er07999 · Jan 1, 2005

I have also heard of this. It was also on a very high powered dsm. The link still didn't yield a good answer, or any sort of before and after power comparison. I would like to hear more about this if anyone has done it. I don't see how increasing the overlap time would yeild more power someone please clear this up. :thumb:

Maglin · Jan 1, 2005

Increasing valve overlap increases top end power as the exhaust gases go out and the intake is comeing it the exhaust actually pulls the intake charge in. In the lower rpm range it really effects power output drasticly. You've heard those very loopy V-8's barely idleing around. That is from excessive valve overlap. It kills idle vaccume. I think for a drag stand point w/ a hugh turbo retarding the exhaust cam one tooth is very advantagous for the budget minded.

bastarddsm · Jan 1, 2005

Overlap on a turbo engine is bad! high rpm n/a motor like overlap becuase it help scavanging.

Maglin · Jan 1, 2005

I was thinking the same thing about overlap. But I would give it a go and see what happens. I have no clue what the overlap is stock. The added heat from opening up the exhaust valves sooner could help the turbo spool.

1fast97gsx · Jan 2, 2005

I will retard it 4 -5 degrees and let you know how it goes. Top end is all I am really looking for and it beats spending $600 on good cams when I plan to sell the car within a few months anyways. I'll keep everyone posted ... should be running in 2-3 weeks.

DSM007 · Jan 2, 2005

retarding the exhaust cam by moving it over one tooth seemed like a bad idea to me and a buddy of mine....when we kinda guessed looking at how much it would move compared to the marks on his AEM cam gears it would come out to about 7 degress moving the belt over one tooth on the exhaust cam....this was brought up as a question on dsmtalk about 3 1/2 years ago and we posted a reply on it.......I wouldnt do it to my engine but you can try it if ya want to....I would like to see the results

............joking....well anyways so ya wanna do something cheap for your motor and ya cant afford cams?....heres a little thing we found out with the AEM cam gears on stock cams....my buddy bought them cause he saw a deal on ebay...he installed them...pain in the ass he said by the way tryin to get the old gears off although LOL

...well he got them installed and went down the road tuning them....no all wheel drive dyno in the area so it was seat of the pants tuning....46 trim compressor wheel in a 20G compressor housing turbo clipped 15 degrees..internal wastegate....o2 eliminator downpipe....3 turbo back no cat....AFC...pocket logger....TMO ECU...spearco 216.. 660's...yada,yada,yada....well we found out playin with the intake side made no power what so ever...but the exhaust side retarding it 2 to 3 degrees made quite a bit of top end power with no loss in low end power..he even had that race cam burbly off idle sound like race cams LOL

.....he was makin very close to 500hp at the crank on stock cams with this setup and his spool was no different than a big 16G.....so for you guys on a budget and you wanna make power on stock cams and cant afford cams....just get an AEM cam gear for the exhaust side and retard it 2 to 3 degrees and you will have what ya been lookin for :thumb:

1fast97gsx · Jan 2, 2005

DSM007 said:
retarding the exhaust cam by moving it over one tooth seemed like a bad idea to me and a buddy of mine....when we kinda guessed looking at how much it would move compared to the marks on his AEM cam gears it would come out to about 7 degress moving the belt over one tooth on the exhaust cam....this was brought up as a question on dsmtalk about 3 1/2 years ago and we posted a reply on it.......I wouldnt do it to my engine but you can try it if ya want to....I would like to see the results ............joking....well anyways so ya wanna do something cheap for your motor and ya cant afford cams?....heres a little thing we found out with the AEM cam gears on stock cams....my buddy bought them cause he saw a deal on ebay...he installed them...pain in the ass he said by the way tryin to get the old gears off although ...well he got them installed and went down the road tuning them....no all wheel drive dyno in the area so it was seat of the pants tuning....46 trim compressor wheel in a 20G compressor housing turbo clipped 15 degrees..internal wastegate....o2 eliminator downpipe....3 turbo back no cat....AFC...pocket logger....TMO ECU...spearco 216.. 660's...yada,yada,yada....well we found out playin with the intake side made no power what so ever...but the exhaust side retarding it 2 to 3 degrees made quite a bit of top end power with no loss in low end power..he even had that race cam burbly off idle sound like race cams .....he was makin very close to 500hp at the crank on stock cams with this setup and his spool was no different than a big 16G.....so for you guys on a budget and you wanna make power on stock cams and cant afford cams....just get an AEM cam gear for the exhaust side and retard it 2 to 3 degrees and you will have what ya been lookin for

Thanks for the info ... I have a built motor with the only stock part being the cams. The reason for that is I decided on selling the car, so I didn't want to spend another $600 for cams. I have a set of fidanza gears though which are already installed on the stock cams, so I will do what you said and retard the exhaust cam 3 degrees. Thanks for the info.

Matts95TSiAWD · Jan 2, 2005

please let us know your results. :talon:

Mirage2LTurbo · Jan 2, 2005

1 tooth = 6 degrees cam speed I believe. Eric retarded my cam one degree back in the day, seemed to pull better.

Also, to the guy that said overlap on turbo cars is bad, where did you pull that from? Out of your ass?

redrkt · Jan 2, 2005

Retarding the exhaust cam 1 tooth equals 7.5 cam degrees. Doing this will basically shift your power curve up higher, so you might feel some loss of midrange power. It's supposed to make 7-10 more hp from ~6k to 7.5k than the stock cam timing. I did it on my car and picked up 1-2 mph consistently at the track. Best was 11.98 @ 115 on a small 16g. It didn't seem to affect spool much either, but it is only a 16g.

You have to keep in mind though, that everyones setup is different, so everyone might not get the same results from it. Tuning is always a trial and error process.

bastarddsm · Jan 2, 2005

Mirage2LTurbo said:
1 tooth = 6 degrees cam speed I believe. Eric retarded my cam one degree back in the day, seemed to pull better.

Also, to the guy that said overlap on turbo cars is bad, where did you pull that from? Out of your ass?

Dude get your head outa your ass and think about it. if the intake is open when the exhaust is open then it is going to try and blow the exhaust gasses out the intake.

Black94TSI · Jan 2, 2005

bastarddsm said:
Dude get your head outa your ass and think about it. if the intake is open when the exhaust is open then it is going to try and blow the exhaust gasses out the intake.

So you mean my custom cammotion ground 249/240 @ .050 114 LSA turbo cam with 8 degrees of overlap @ .050 is all wrong? It should spool the turbo very late? You should call up Cammotion, maybe Ed Curtis @ Flowtech too, and tell them that their 30+ years of building turbo motors and grinding turbo camshafts is all wrong, that having zero or negative overlap is the only way to have a fast turbo motor.

95blackGsTurbo · Jan 2, 2005

He's right. Plus if YOU think about it. The turbo will be spinning so the exhaust will be sucked out so fast it wouldn't have time to go out the intake. Plus it shouldn't go out the intake valve anyways because the air in there is comming in a such a rate of speed.

Mirage2LTurbo · Jan 2, 2005

Black94TSI said:
So you mean my custom cammotion ground 249/240 @ .050 114 LSA turbo cam with 8 degrees of overlap @ .050 is all wrong? It should spool the turbo very late? You should call up Cammotion, maybe Ed Curtis @ Flowtech too, and tell them that their 30+ years of building turbo motors and grinding turbo camshafts is all wrong, that having zero or negative overlap is the only way to have a fast turbo motor.

Not to mention, I doubt that guy even has specs on the popular cams we run.

Also, replying to bastards post, if both valves were open, given you aren't running a 14b housing and wheel on a Green, the intake would have positive pressure over the exhaust, so why would exhaust go back into the intake? That would be some massive backpressure.

AUTOMECH01 · Jan 3, 2005

95bLaCkGsTuRbO said:
He's right. Plus if YOU think about it. The turbo will be spinning so the exhaust will be sucked out so fast it wouldn't have time to go out the intake. Plus it shouldn't go out the intake valve anyways because the air in there is comming in a such a rate of speed.

if i am not wrong on a 4 cycle engine the only time both in and ex are open at the same time is when the piston is in the bottom of the bore?

1fast97gsx · Jan 4, 2005

AUTOMECH01 said:
if i am not wrong on a 4 cycle engine the only time both in and ex are open at the same time is when the piston is in the bottom of the bore?

CanadianTalon · Jan 5, 2005

Food for thought.

Stock Honda B16 cams have 4.2 degrees of overlap. Stock Integra Type-R cams have 8.9 degrees of overlap. A swap from B16 to ITR cams is worth a good amount of power on a turbo car, figure 5-8% with no change in boost. I swapped to ITR cams in my old car, and the lower I knocked down the VTEC crossover the quicker boost came on.

1fast97gsx · Jan 5, 2005

CanadianTalon said:
the lower I knocked down the VTEC crossover the quicker boost came on.

ooh!

.. I want VTEC :laugh:

espinelli · Jan 5, 2005

Retarding the exhaust cam will help the cars mid range power. In addition, it will also help reduce your lag. Especially for the guys running big turbos.

I would think that most of the guys running huge turbos and big cams would do this mod.

myblack98gst · Jan 5, 2005

I am fairly certain I know the answer here but I want to check... as you are looking at the cam gears:

turning clockwise would retard
turning counter-clockwise will advance

correct??

jo1 · Jan 28, 2005

myblack98gst said:
I am fairly certain I know the answer here but I want to check... as you are looking at the cam gears:

turning clockwise would retard
turning counter-clockwise will advance

correct??

turning clockwise would advance
turning counter-clockwise will retard

tighty · Jan 28, 2005

Just need clarification on a few things for this. Is it okay/beneficial to do it on a mostly stock car or will it just help those with larger turbos?

1fast97gsx · Jan 28, 2005

to me it seems more of a big turbo thing. I'll let you all know how it works out. I had a few obstacles along the way but the engine and trans are going in this weekend ... all I need to do then is make intercooler pipes.

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retarding stock exhaust cam?

1fast97gsx

1fast97gsx

Sk8er07999

Maglin

bastarddsm

Maglin

1fast97gsx

DSM007

1fast97gsx

Matts95TSiAWD

Mirage2LTurbo

redrkt

bastarddsm

Black94TSI

95blackGsTurbo

Mirage2LTurbo

AUTOMECH01

1fast97gsx

CanadianTalon

1fast97gsx

espinelli

myblack98gst

jo1

tighty

1fast97gsx

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