Interesting case of problems on the dyno
Interesting case of problems on the dyno
Last week we had a customer come in with an EVO8. I was to tune the car using AEM EMS.
This is the basic build of the car:
Switzer built 2 liter
Buschur Racing Stage 3 cylinder head
3" turbo back exhaust (not ours, JDM style pointing out to the side)
Stock uppper i/c pipe with a Tial BOV welded to it.
Stock intake/tb
Kelford 272 cams
Home made twin pump set up
HKS DLI2 ignition
AMS 3.5" FMIC
FP Red with new 4" inlet cover
Lower i/c pipe of some kind
PTE 1200 cc injectors
E85
I spent quite a bit of time on the car last week but just could not pull any good power out of the car. At 28 psi of boost the car was just done and the power was only at 395 with torque at 408. I knew something wasn't right, the knock counts were also very high on the car, even when running it out of boost. The owner and I talked about it and eventually he said he had used a set of 2G DSM cam gears on it............not good. The 2G gears are off about 1 full tooth, that means the cams were running advanced about 7 degrees. The car was taken off the dyno and stock gears were put back on it by the owner of the car.
Today the car came back into the shop. The very first pull was up by 53 whp and torque increased by 1 ft lb. The entire curve was shifted to the right by about 500 rpm.
Here is the dyno sheet of the before and after from just putting the correct cam gears on the car, NO additional tuning at all.
The tune that was in the car with the wrong cam gears had the car running at 11.5:1 from 3500 to 7500 rpm, more or less anyway. After the cam gears were fixed the AFR's under 6300 rpm were buried at 10:1 and then after that went as lean as 13.5:1.
The knock counts were non existent after the fix of the cam gears and after some additional tuning the car left with 488 whp and 471 ft lbs at 32 psi.
Here is a before and after graph of the car with the wrong cam gears and then with the correct gears and the final tune. Keep in mind that the base tune was the MOST power I could get out of the car with the cams installed incorrectly.
This is the basic build of the car:
Switzer built 2 liter
Buschur Racing Stage 3 cylinder head
3" turbo back exhaust (not ours, JDM style pointing out to the side)
Stock uppper i/c pipe with a Tial BOV welded to it.
Stock intake/tb
Kelford 272 cams
Home made twin pump set up
HKS DLI2 ignition
AMS 3.5" FMIC
FP Red with new 4" inlet cover
Lower i/c pipe of some kind
PTE 1200 cc injectors
E85
I spent quite a bit of time on the car last week but just could not pull any good power out of the car. At 28 psi of boost the car was just done and the power was only at 395 with torque at 408. I knew something wasn't right, the knock counts were also very high on the car, even when running it out of boost. The owner and I talked about it and eventually he said he had used a set of 2G DSM cam gears on it............not good. The 2G gears are off about 1 full tooth, that means the cams were running advanced about 7 degrees. The car was taken off the dyno and stock gears were put back on it by the owner of the car.
Today the car came back into the shop. The very first pull was up by 53 whp and torque increased by 1 ft lb. The entire curve was shifted to the right by about 500 rpm.
Here is the dyno sheet of the before and after from just putting the correct cam gears on the car, NO additional tuning at all.
The tune that was in the car with the wrong cam gears had the car running at 11.5:1 from 3500 to 7500 rpm, more or less anyway. After the cam gears were fixed the AFR's under 6300 rpm were buried at 10:1 and then after that went as lean as 13.5:1.
The knock counts were non existent after the fix of the cam gears and after some additional tuning the car left with 488 whp and 471 ft lbs at 32 psi.
Here is a before and after graph of the car with the wrong cam gears and then with the correct gears and the final tune. Keep in mind that the base tune was the MOST power I could get out of the car with the cams installed incorrectly.
Dave,
Interesting data. Why do think there was that drastic a change in AFRs below 6300? Above I understand as the engine was actually getting some air with the overlap dropped back to where it should be.
Interesting data. Why do think there was that drastic a change in AFRs below 6300? Above I understand as the engine was actually getting some air with the overlap dropped back to where it should be.
Trending Topics
He didn't have the stock sprockets after taking off the adjustable gears and assumed they were the same.
John, if you look at the first sheet the low end the car had with the cams installed incorrectly was a LOT more than with the cams installed correctly. As you know more power is more fuel so when the cams were installed correctly it moved the curve to the right and with the loss of low end power came a richer fuel mixture.
John, if you look at the first sheet the low end the car had with the cams installed incorrectly was a LOT more than with the cams installed correctly. As you know more power is more fuel so when the cams were installed correctly it moved the curve to the right and with the loss of low end power came a richer fuel mixture.
I spent quite a bit of time on the car last week but just could not pull any good power out of the car. At 28 psi of boost the car was just done and the power was only at 395 with torque at 408. I knew something wasn't right, the knock counts were also very high on the car, even when running it out of boost. The owner and I talked about it and eventually he said he had used a set of 2G DSM cam gears on it............not good. The 2G gears are off about 1 full tooth, that means the cams were running advanced about 7 degrees.
7.5 degrees at the cam gears is 15 degrees at the crank, and that's a lot!
What you can see is the effect of advancing the cams had on the powerband. It spooled the turbo much faster and generated the same torque, but almost 500 rpm earlier.
Bringing the cams back to the manufacturer's base timing moved the torque curve to the right. And since HP is a function of torque with respect to rpm, the same torque higher in the rpm range = more hp.
If you take adjustable cam gears, and this time retard both intake and exhaust cams, you should see the torque curve move a little higher in the rpm range, and power should go up again (if you're not out of turbo).
What you can see is the effect of advancing the cams had on the powerband. It spooled the turbo much faster and generated the same torque, but almost 500 rpm earlier.
Bringing the cams back to the manufacturer's base timing moved the torque curve to the right. And since HP is a function of torque with respect to rpm, the same torque higher in the rpm range = more hp.
If you take adjustable cam gears, and this time retard both intake and exhaust cams, you should see the torque curve move a little higher in the rpm range, and power should go up again (if you're not out of turbo).
7.5 degrees at the cam gears is 15 degrees at the crank, and that's a lot!
What you can see is the effect of advancing the cams had on the powerband. It spooled the turbo much faster and generated the same torque, but almost 500 rpm earlier.
Bringing the cams back to the manufacturer's base timing moved the torque curve to the right. And since HP is a function of torque with respect to rpm, the same torque higher in the rpm range = more hp.
If you take adjustable cam gears, and this time retard both intake and exhaust cams, you should see the torque curve move a little higher in the rpm range, and power should go up again (if you're not out of turbo).
What you can see is the effect of advancing the cams had on the powerband. It spooled the turbo much faster and generated the same torque, but almost 500 rpm earlier.
Bringing the cams back to the manufacturer's base timing moved the torque curve to the right. And since HP is a function of torque with respect to rpm, the same torque higher in the rpm range = more hp.
If you take adjustable cam gears, and this time retard both intake and exhaust cams, you should see the torque curve move a little higher in the rpm range, and power should go up again (if you're not out of turbo).
So with that said it proves that adjustable cam gears ARE a benefit. Many tuners say they arent worth the money however....
Obviously you can move the power around by moving cam gears, I hate cam gears, we don't sell them unless someone absolutely insists on wanting them. I prefer to have a cam ground to make power where we want it and run them straight up.
The results of what happened aren't "interesting" to me or surprising, I posted this figuring many of the rest of you may benefit from it or find it interesting.
The results of what happened aren't "interesting" to me or surprising, I posted this figuring many of the rest of you may benefit from it or find it interesting.