My buddy Smartbomb installed Cosworth 272 cams with springs/retainers. We wanted to see how much power was gained from the cams and to tune the car for the cams. Just as a refresher the car has the following mods:

Works Downpipe
Works O2 Housing
Greddy Ti Exhaust
Test Pipe
ARC Intake Box
ECU boost control #65 pill
XS Engineering 3.5 Inch Intercooler
XS Engineering LICP/UICP
1000 cc RC injectors
Self-ported intake manifold
Works throttle body
Full-Race tubular exhaust manifold
Samco intake pipe hose

SB’s aim is to keep adding bolt-on mods and see if the car can hit 400 whp with the stock turbo on 91 octane pump gas. Adding the Cosworth cams was the next step in the process.

This was an easy tune. We took the car to the Looney Tuning proving grounds and logged the tune as is. The boost was ~0.5 psi lower with the cams than w/o the cams, even though the weather conditions were close. Regardless, I did not add more boost since I wanted to see how the cams performed without messing around with the tune. Had I added that half a psi of boost we would have extract even more power from the cams.



Another change was the AFR. The AFR was slightly richer at the bottom and top ends, but slightly leaner in the mid range. The changes were very small, so it was not worth it to change them.



The one parameter that really changed was the knock. Here is the way the knock looked like with the cams:



Most of the knock was concentrated at the top end. Keep in mind that this car was running about 15* ignition timing advance by redline with advanced cam timing in the mivec map at the top end. Generally, cammed cars require less ignition advance than non-cammed cars. My guess was reducing the ignition advance by 1-2* would cure the knock on the car. But before we did this, we wanted to see if the knock could be cured by retarding the mivec advance at the top end. So we reduce mivec advance by 6-10* from 5500-6500 rpm and zeroed the mivec map by 7000 rpm and re-logged. Alas, it did not work and the car still knocked.

So we pulled over and removed the necessary ignition timing and logged again. That did the trick. Knock was reduced to about 1-2 counts. I can live with that for the time being, since this car is in constant flux and will be re-tune multiple times before we are done with it. We ended up with the following knock profile:



What about the power gains? Here is what the car scored on DLL before and after the cams. The weather conditions were as follows:

Baseline: Temp 21*C, Humidity 63%, Baro 101
Cams run: Temp 26*C, Humidity 57%, Baro 101



As always DLL proved consistent with the 4 minute apart runs within 1-2% of each other:

 

Nice writeup!

 

How does the car feel to drive compared to b4?

I have heard some cams make drivability worse... Sure you get bigger dyno numbers/peak power at redline, but around town is worse..

Comments?

 

The car drives really well. The car did not lose a lot at the low end. We are running a lot of cam timing advance at the low end based on the map that I posted in the mivec thread. Another thing is that we are running about 3-4* ignition timing advance in the cruise/low areas. That help low end around town driveability.

We increased the idle and increased the ignition timing at idle. So the car idles nicely, not like stock, but close. Hopefully, we will not get a CEL with all the mivec advance and ignition advance at the low end.

 

The cams didn't push the peak torque back? How is that? Maybe some evo9 thing. The mivec?

Thanks for the writeup.

 

Are you going to increase the boost to match the values with the stock cams?

 

Ya better! bump that torque up a little!

tephra, cams shouldn't really hurt driveability, especially on an IX.

 

The boost was ~0.5 psi less across the rpm range. I did not add more boost with the cams. Had I done that, the Tq would go slightly higher. The point of adding 272+ cams is to increase HP and not TQ.

 

I might do that, but it is going to be tricky to add 0.5 psi w/o going over that number. Plus, the WGDC is now maxed at the top end. The car will get a number 67 pill and a boost re-tune. I will post the results.

 

Great write up. I just had my M2's installed this weekend, and I can't wait to get tuned.