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Dyno sheets. What next?

turbotankshane

Active member
Joined
Aug 3, 2010



Made a trip to the dyno today. The red graph is from about a year ago, car was at 300K with just 2.5" exhaust. Blue graph is from today with same exhaust, gutted airbox/k&n with extra cold air pipe routed to front bumper, 15g @ 12psi, IPD cam @ +2.5, TLAO chips.
It was nice to verify a decent gain by other means than butt dyno. Made a few pulls, in 2nd and 3rd, 2nd gear was used for the graph shown.
I noticed on the dyno I seemed to get a backfire right as boost peaks, but AFRs were perfect the entire time, so it leads me to think timing may be too advanced? I have no way to mess with the tune right now, just looking for input.
I'm looking to get a 250+hp setup from this car. I don't really like the way the power is falling after 5k, so I may run the cam straight up soon and see if it helps. I'm sure the stock downpipe is choking flow as well, so I plan to get a new 2.5" dp made to match diameter of the rest of the exhaust.
So current plans include 2.5" dp, bigger intercooler, and I have a 4bar fpr ready to go in and plan to run 15psi. Think this should reach my goals?
 
What it looks like to me,

Your wastgate allowed a little over boost notice the spike at the start then a drop. Notice a spike in the a/f ratio at the same time? You caused a momentary lean condition at that point. Not major, what boost controler are you using?

Always start tuning a car with stock cam timing. With the amount of smoothing and the choppiness of the graph, you may be have some issue in the cam set up or spark plugs getting blown out. A good a/f ratio does not always dictate no knock. Check the plugs for signs of pinging. Small pepper specks on the plugs.

Something else to add, if I remember right, the distributor on the 740 is attached to the back of the cam. When you changed the cam timing, did you reset the ignition timing? This is over looked often on these time of set ups. You advance the cam timing and advance the ignition as well(correct me if I am wrong on this could be retarding it)

You have a good set up. A little fine tuning will do wonders before throwing more parts at it.
 
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Do not waste your time with a 2.5" exhaust.

Go 3" on the downpipe and cat (if you ar egoing to run a cat) from there you can stay 2.5" exhaust but 3" is recommended.

An intercooler will help a ton also over the entire powerband.

No need for more fuel just yet as you are still plenty rich under load.

3" downpipe, NPR or Ebay IC and turn the boost up to 16psi. Those alone should put you near 200whp.
 
Did you port the exhaust manifold outlet when you swapped turbos?

Looks kind of like my dyno "curves" when I had a bad head gasket- check compression lately at 300+K?
 
Do not waste your time with a 2.5" exhaust.

Go 3" on the downpipe and cat (if you ar egoing to run a cat) from there you can stay 2.5" exhaust but 3" is recommended.

An intercooler will help a ton also over the entire powerband.

No need for more fuel just yet as you are still plenty rich under load.

3" downpipe, NPR or Ebay IC and turn the boost up to 16psi. Those alone should put you near 200whp.

+1

The down pipe is where the exhaust is still extremely hot so the extra volume will allow for better evacuation.
 
What it looks like to me,

Your wastgate allowed a little over boost notice the spike at the start then a drop. Notice a spike in the a/f ratio at the same time? You caused a momentary lean condition at that point. Not major, what boost controler are you using?

Always start tuning a car with stock cam timing. With the amount of smoothing and the choppiness of the graph, you may be have some issue in the cam set up or spark plugs getting blown out. A good a/f ratio does not always dictate no knock. Check the plugs for signs of pinging. Small pepper specks on the plugs.

Something else to add, if I remember right, the distributor on the 740 is attached to the back of the cam. When you changed the cam timing, did you reset the ignition timing? This is over looked often on these time of set ups. You advance the cam timing and advance the ignition as well(correct me if I am wrong on this could be retarding it)

You have a good set up. A little fine tuning will do wonders before throwing more parts at it.
Hmm. I see that spike on the curve now. I think I'm going to run the cam straight up and see if it helps. I think the cam being advanced, paired with the advanced timing of the chips, may be causing spark blow out. I'm using bpr7es plugs set to factory gap, with fairly new wires, rotor/cap and coil, so I know plugs are up to the task. If that doesn't help I may just try a little bigger gap on the plugs.
I was under the impression that the EZK controlled ignition timing advance, so I don't believe I advanced ignition timing when I advanced cam timing.
 
Did you port the exhaust manifold outlet when you swapped turbos?

Looks kind of like my dyno "curves" when I had a bad head gasket- check compression lately at 300+K?

I did no porting when I swapped the turbos. I'm thinking I will soon because my manifold has developed a small crack.
I checked compression around the time the first curve was made. Cyl #3 was a little weaker than the rest but still within spec. Other three were great. The car now has 311k and hasn't been beat on daily so I think compression should still be good.
 
Do not waste your time with a 2.5" exhaust.

Go 3" on the downpipe and cat (if you ar egoing to run a cat) from there you can stay 2.5" exhaust but 3" is recommended.

An intercooler will help a ton also over the entire powerband.

No need for more fuel just yet as you are still plenty rich under load.

3" downpipe, NPR or Ebay IC and turn the boost up to 16psi. Those alone should put you near 200whp.

3" pipes and intercooler are next on the to do list.
 


You may want to check everything make sure its not off a tooth or leaking boost or anything. This is my dyno pull lh2.4 no chips +3 ignition mod with stock downpipe, ebay ic, and 2.5 side exhaust. 15g on 16lbs. So no chips or cam but I made more power still blowing black smoke Cause it was so dang rich. That was done with a blown head gasket
 


You may want to check everything make sure its not off a tooth or leaking boost or anything. This is my dyno pull lh2.4 no chips +3 ignition mod with stock downpipe, ebay ic, and 2.5 side exhaust. 15g on 16lbs. So no chips or cam but I made more power still blowing black smoke Cause it was so dang rich. That was done with a blown head gasket

What cam was that with?
 
3" pipes and intercooler are next on the to do list.

Why 3" intercooler piping? Its over kill to say the least. The thing is the turbo has to fill the volume of the intercooler and the piping and larger diameter piping with a small compressor hurts the air velocity. Use 2.5" piping to keep the velocity up. I have seen cars with over 500awhp do just fine with 2.5" tubing. The only advantage of 3" over 2.5" is if there is a bunch of tight radius bends.


My other car is 1999 A4 with a gt3071r and I run 2.25" hotside of Intercooler and 2.5" coldside. Never an issue.
 
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The 3" intercooler plumbing isn't going to hurt anything, it will only help. You won't feel a difference in the time it takes to pressurize that volume, and it's not going to hurt velocity.
 
Why 3" intercooler piping? Its over kill to say the least. The thing is the turbo has to fill the volume of the intercooler and the piping and larger diameter piping with a small compressor hurts the air velocity. Use 2.5" piping to keep the velocity up. I have seen cars with over 500awhp do just fine with 2.5" tubing. The only advantage of 3" over 2.5" is if there is a bunch of tight radius bends.


My other car is 1999 A4 with a gt3071r and I run 2.25" hotside of Intercooler and 2.5" coldside. Never an issue.

My communication skills are getting worse. I meant 3" exhaust, or at least 3" downpipe, and an upgraded intercooler are next on the list.
However, since you planted the idea, I guess upgrading the tubing should be in order as well. Where's the best place to order bigger intercooler piping?
 
The 3" intercooler plumbing isn't going to hurt anything, it will only help. You won't feel a difference in the time it takes to pressurize that volume, and it's not going to hurt velocity.

Have you actually tried this? I have and the first thing I will tell you is my gt3071r spools faster then several gt2871r builds on the exact same engine. I am actually using the odd ball gt3071r wg version with .86 housing and 90 trim turbine and I am still doing better then others with the same tune and I am using 2.5" exhaust to their 3" exhaust.

Any amount of air forced through a smaller pipe compared to a bigger pipe will have a greater velocity as long as the pipe is not to small to cause a restriction. The tircks with intercooler piping is to use the shortest amount possible and the smallest size possible without causing a restriction.
 
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My communication skills are getting worse. I meant 3" exhaust, or at least 3" downpipe, and an upgraded intercooler are next on the list.
However, since you planted the idea, I guess upgrading the tubing should be in order as well. Where's the best place to order bigger intercooler piping?

On DP and exhaust you want either the same size dp and exhaust or a larger dp then exhaust. The exhaust gas at the DP is extremely hot and will need area to expand back too post turbine. It cools considerable from the DP to exhaust.
 
Stock t cam and stock cam gear. Ported manifold and exh housing but im not sure its worth that much power.

I'm sure it's worth a little bit on the top end. And I see the same spike on your curve as boost comes on, maybe it's the hallman boost controller i'm using.
I think running the cam straight up and with the extra flow/reduced pressure drop from a better intercooler, I should see a lot better performance.
 
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