I LOST 20ftlbs. And 5 hp!
I LOST 20ftlbs. And 5 hp! Well I switched my complete exhaust from Mac Mids and a flowmaster, to Speed Engineering long tubes and the new Texas Speed cat back. So I decided to go for a retune, same outside temp. as the first tune, same tuner, same dyno. Well I LOST 20ftlbs and 5hp with this new setup. My tuner was baffled. The only thing he could think was a bad header design. So I am putting the Mac Mids back on and am going to go back sometime next week to see if there is any difference.
How long between the runs? SAE correction? Temp isn't the only factor in the dyno calculations.
Seriously doubt you lost that much torque unless there is some kind of problem somewhere.
If you do switch back and dyno again post both graphs.
Seriously doubt you lost that much torque unless there is some kind of problem somewhere.
If you do switch back and dyno again post both graphs.
Long tubes aren't really much of an upgrade from mac miss if your car only has bolt ons. It still should be about a 5whp gain with some loss in torque on the top end. My 98 M6 car with Mac mid's and a cutout was around 340whp
How much time passed between dyno runs?
Changes to the tune?
Same dyno?
STD or SAE graph?
Anything else done to the car between dyno runs Like plugs or wires?
I don't buy it for a second....but I would believe a spark plug has a cracked porcelein or something.
Changes to the tune?
Same dyno?
STD or SAE graph?
Anything else done to the car between dyno runs Like plugs or wires?
I don't buy it for a second....but I would believe a spark plug has a cracked porcelein or something.
The first dyno was almost exactly one year ago, same type of a day almost the same temp. No other changes than the exhaust. The tuner said the engine ran perfect! He could not see any issues with anything. He is a very reputable tuner. Mike at New Era Performance in Rochester NY. He only specializes in LS cars and was flown to Dubai to tune a customers car. I will post the graphs when I get home. Same dyno, same tuner.
The first dyno was almost exactly one year ago, same type of a day almost the same temp. No other changes than the exhaust. The tuner said the engine ran perfect! He could not see any issues with anything. He is a very reputable tuner. Mike at New Era Performance in Rochester NY. He only specializes in LS cars and was flown to Dubai to tune a customers car. I will post the graphs when I get home. Same dyno, same tuner.
There are many variables, was there any logging of
(say) AFR, delivered spark advance, etc. the first
time or the second?
I would have a look inside the new Y, I once bought
an older version TSP Y which had heinous tube-into-
tube stick-in (not a good merge); a Jet-Hot Y was
nearly as bad, tube-into-tube styles look prone to
cause reversion from one side up the other. I do not
know what new TSP exhaust products look like. But
stare down the Y from the back end and see if there
is anything blocking the bore, or if one tube enters
at near right angle to the other (bad - exhaust
should only change direction in smooth bent tube
and by the time two become one, both should be
going in the same direction).
Catback muffler restrictions are another possible
difference, you might find data on the two. But
I can't say it's likely.
Then there is the question whether second time
results are "tuned to best" or "gave it a shot".
If there weren't multiple pulls with tweaks in
between, call it "gave it a shot". Change the
exhaust, change the VE, change the fuel and
spark that put the motor at best output -
expect there to be some cut-and-try, to get
optimized.
(say) AFR, delivered spark advance, etc. the first
time or the second?
I would have a look inside the new Y, I once bought
an older version TSP Y which had heinous tube-into-
tube stick-in (not a good merge); a Jet-Hot Y was
nearly as bad, tube-into-tube styles look prone to
cause reversion from one side up the other. I do not
know what new TSP exhaust products look like. But
stare down the Y from the back end and see if there
is anything blocking the bore, or if one tube enters
at near right angle to the other (bad - exhaust
should only change direction in smooth bent tube
and by the time two become one, both should be
going in the same direction).
Catback muffler restrictions are another possible
difference, you might find data on the two. But
I can't say it's likely.
Then there is the question whether second time
results are "tuned to best" or "gave it a shot".
If there weren't multiple pulls with tweaks in
between, call it "gave it a shot". Change the
exhaust, change the VE, change the fuel and
spark that put the motor at best output -
expect there to be some cut-and-try, to get
optimized.
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Verdad Gallardo There were 3 pulls in all with tweaks in between. He gave me a print out of the 3 pulls but I was so frustrated I threw them out. This pic is all I have. I plan on putting the Macs on this weekend and hopefully get back for another go at it next week. I guess which ever system does the best will stay on.
1 of those graphs was SAE and the other was STD. 1 of those had smoothing set on 1, the other on 5. They weren't revved the same. I would go chuck the SE stuff until you dig in a little more.
Sorry I'm a noob when it comes tuning, I don't have a clue on how that can affect things. If you can school me a little I would appriciate it. I can sure turn some wrenches though!
STD is a graph of THAT car on THAT day. You convert it to SAE as it is the great neutralizer so that you can compare any car on any day. Smoothing turned up will also affect how a graph looks. All I'm saying is you don't have an apples to apples comparison so don't go throwing out the SE stuff. People have shown time and again even a stock LS1 will pick up power everywhere with larger headers.
STD is a graph of THAT car on THAT day. You convert it to SAE as it is the great neutralizer so that you can compare any car on any day. Smoothing turned up will also affect how a graph looks. All I'm saying is you don't have an apples to apples comparison so don't go throwing out the SE stuff. People have shown time and again even a stock LS1 will pick up power everywhere with larger headers.
I looks looked at the graphs again and the were both on 5 for smoothing. I did some research and got my answer for the SAE and STD conversion. The tq curve looks flatter on the one with the LTs. I'm confused on what to do. I may still switch back to the Macs just to see what happens.
I had a similar issue when I switched from 1 3/4 Stainless Works long tube headers to 1 7/8" Speed Engineering headers. I picked up torque, lots of it, but lost HP on the big end. With the bigger headers, power started dropping off way before it did with the old Stainless Works 1 3/4" setup. With both headers I was running Texas Speed true duals. After much debate and discussion, we determined it was the valve events of the cam. Here is the thread if you'd like to see it.
https://ls1tech.com/forums/dynamomet...-431-rwtq.html
Since then, the car has a new custom cam which was spec'd around the heads. The issue ended up being that the cam valve events did not jive with the exceptional exhaust flow the heads have. Adding the bigger headers which expel more air only made the issue worse on the big end. All of this was through a LS6 intake mind you. After the cam change, the car picked up torque and HP everywhere and carries power well past 6,000 rpms. Something like this could be your issue.
https://ls1tech.com/forums/dynamomet...-431-rwtq.html
Since then, the car has a new custom cam which was spec'd around the heads. The issue ended up being that the cam valve events did not jive with the exceptional exhaust flow the heads have. Adding the bigger headers which expel more air only made the issue worse on the big end. All of this was through a LS6 intake mind you. After the cam change, the car picked up torque and HP everywhere and carries power well past 6,000 rpms. Something like this could be your issue.
I had a similar issue when I switched from 1 3/4 Stainless Works long tube headers to 1 7/8" Speed Engineering headers. I picked up torque, lots of it, but lost HP on the big end. With the bigger headers, power started dropping off way before it did with the old Stainless Works 1 3/4" setup. With both headers I was running Texas Speed true duals. After much debate and discussion, we determined it was the valve events of the cam. Here is the thread if you'd like to see it.
https://ls1tech.com/forums/dynamomet...-431-rwtq.html
Since then, the car has a new custom cam which was spec'd around the heads. The issue ended up being that the cam valve events did not jive with the exceptional exhaust flow the heads have. Adding the bigger headers which expel more air only made the issue worse on the big end. All of this was through a LS6 intake mind you. After the cam change, the car picked up torque and HP everywhere and carries power well past 6,000 rpms. Something like this could be your issue.
https://ls1tech.com/forums/dynamomet...-431-rwtq.html
Since then, the car has a new custom cam which was spec'd around the heads. The issue ended up being that the cam valve events did not jive with the exceptional exhaust flow the heads have. Adding the bigger headers which expel more air only made the issue worse on the big end. All of this was through a LS6 intake mind you. After the cam change, the car picked up torque and HP everywhere and carries power well past 6,000 rpms. Something like this could be your issue.
What are those cam specs? Do you have any flow numbers for the heads? Those two things could help me determine if that's your issue.
This is what Cam Motion stated about the old cam I had and why I was having the issue. That's why I'd like to see the cam specs, particularly the valve events.
In looking at your current camshaft, it is pretty obvious why the power does not carry well in the upper RPM. Your current camshaft closes the intake valve at 38.5 degrees after bottom dead center. This is really early for a performance camshaft in an LS1 like yours and is about the same as a stock cam LS1 camshaft.
This is what Cam Motion stated about the old cam I had and why I was having the issue. That's why I'd like to see the cam specs, particularly the valve events.
In looking at your current camshaft, it is pretty obvious why the power does not carry well in the upper RPM. Your current camshaft closes the intake valve at 38.5 degrees after bottom dead center. This is really early for a performance camshaft in an LS1 like yours and is about the same as a stock cam LS1 camshaft.
Last edited by Rise of the Phoenix; Apr 14, 2017 at 09:09 AM.