lost 20 whp.. what could have been the problem?
06-30-2012, 11:48 PM
#22
its a pretty consistent loss across the bored except for that very small spot between 3200-4000 which its untelling what that can be. you dint specify the different temps your looking at about a 9% drop in power which would equate to about a 20 degree temp difference on days my bet would be on that. otherwise the only possible conclusion could be the tuner isnt running enough spark across the board or is running too much except for that small rpm range and causing spark retard.
you lost power down low which is to be expected from that combo but you went with a better flowing intake(that was with mrev+spacer right?) and cams to match. which means you should be making more power up top. since you made the power before its either weather conditions(my bet now that i see the dyno) or your tuner really fubared your tune.
you lost power down low which is to be expected from that combo but you went with a better flowing intake(that was with mrev+spacer right?) and cams to match. which means you should be making more power up top. since you made the power before its either weather conditions(my bet now that i see the dyno) or your tuner really fubared your tune.
07-01-2012, 01:47 AM
#23
I have S7 cams on my stroker and have good power and torque.
Did you uprade the valves & port the heads? I have Manley large valves and had the heads done.
Sorry you are having problems, I know how frustrating it can be.
Did you uprade the valves & port the heads? I have Manley large valves and had the heads done.
Sorry you are having problems, I know how frustrating it can be.
Last edited by e30cabrio; 07-01-2012 at 01:49 AM.
07-01-2012, 02:39 AM
#25
Now that I am thinking about it, after the stroker went in, my cai which was a Fujita tube from the throttlebody connected to an Injen rubber hose going to an Amsoil filter between the bumper and radiator support. It worked great pre built motor but caused crazy MAF correction costing 20-40 hp on the stroker. When I switched to a Z tube & Pop Charger it all came back.
07-01-2012, 04:52 AM
#26
its a pretty consistent loss across the bored except for that very small spot between 3200-4000 which its untelling what that can be. you dint specify the different temps your looking at about a 9% drop in power which would equate to about a 20 degree temp difference on days my bet would be on that. otherwise the only possible conclusion could be the tuner isnt running enough spark across the board or is running too much except for that small rpm range and causing spark retard.
you lost power down low which is to be expected from that combo but you went with a better flowing intake(that was with mrev+spacer right?) and cams to match. which means you should be making more power up top. since you made the power before its either weather conditions(my bet now that i see the dyno) or your tuner really fubared your tune.
you lost power down low which is to be expected from that combo but you went with a better flowing intake(that was with mrev+spacer right?) and cams to match. which means you should be making more power up top. since you made the power before its either weather conditions(my bet now that i see the dyno) or your tuner really fubared your tune.
07-01-2012, 12:31 PM
#28
headwork isnt going to be a issue not at that low rpm, the heads on our engines have shown to support almost 8k rpms with just cams, springs and retainers at more power then your pushing. plus thats going to further slow down air velocity, the only reason for headwork is to push the absolute limit NA or go for insane power FI.
Last edited by jerryd87; 07-01-2012 at 12:32 PM.
07-02-2012, 07:18 AM
#31
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jerry, 276 down to 263 is only a 4.8% drop in power when i calculate it. Did i calculate it wrong?
That amount of drop is within a standard variant on a dyno. The fact that it's consistent across the entire dyno makes one think that it would be something other than the tune. Error rate in the dyno, ambient temps or humidity, etc.
OP, i know you said the temps stay the same but you are on an island, correct? so humidity can swing day to day. Humidity has a considerable effect on horsepower. Also, do you know if there were any software or firmware updates on the dyno over the past year?
Since the cams were changed, did he tune cam timing? Optimizing cam timing for aftermarket cams in an NA engine is crucial to getting power gains.
That amount of drop is within a standard variant on a dyno. The fact that it's consistent across the entire dyno makes one think that it would be something other than the tune. Error rate in the dyno, ambient temps or humidity, etc.
OP, i know you said the temps stay the same but you are on an island, correct? so humidity can swing day to day. Humidity has a considerable effect on horsepower. Also, do you know if there were any software or firmware updates on the dyno over the past year?
Since the cams were changed, did he tune cam timing? Optimizing cam timing for aftermarket cams in an NA engine is crucial to getting power gains.
07-02-2012, 10:40 AM
#32
nah jeff i wasnt paying attention and went off the untuned number haha
the only thing is that one section where the power is pretty much equal is what kinda struck me as odd i would have thought it would have been everywhere but yah weather can have that big of a impact. very well could be the cam timing as well.
the only thing is that one section where the power is pretty much equal is what kinda struck me as odd i would have thought it would have been everywhere but yah weather can have that big of a impact. very well could be the cam timing as well.
07-02-2012, 10:49 AM
#33
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running that afr in the midrange will definitely have a spark retard event or a "high detonation knock" reducing the amount of timing through redline. i would get him to retune it and also look at his cam timing map.
07-16-2012, 07:33 AM
#37
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If you plan on running out past 6500 then i definitely would go with the blue dyno. The peak numbers mean nothing. That blue dyno holds a considerable more amount of hp up top as well as torque. The red dyno seems to have a little more around the 5500 mark but has quite a bit of drop off in the upper rpm range.
07-16-2012, 01:03 PM
#38
There are tons of factors that come into play, but it could really be anything:
Type of fuel
Humidity
Temp
Dyno variance
Tire type/wear (yes it affects it)
Engine wear/compression
Or it can really come down to who is operating the dyno, and who is doing the tuning compared to last time.
And it's not the gears because that will only affect your torque, not HP
And considering that you lost HP when you installed the MREV2, it leads me to believe that you need head work done. The larger cams are simply not getting the steady amount of air volume that they need. I would consider finding someone to port and polish your heads.
And if you didn't change valve springs during the cam install then you may run into problems down the road....
Type of fuel
Humidity
Temp
Dyno variance
Tire type/wear (yes it affects it)
Engine wear/compression
Or it can really come down to who is operating the dyno, and who is doing the tuning compared to last time.
And it's not the gears because that will only affect your torque, not HP
And considering that you lost HP when you installed the MREV2, it leads me to believe that you need head work done. The larger cams are simply not getting the steady amount of air volume that they need. I would consider finding someone to port and polish your heads.
And if you didn't change valve springs during the cam install then you may run into problems down the road....
07-16-2012, 03:49 PM
#39
So, you lost 2 HP peek with the MREV2? That's correct, you need the shorter runners to get that, but what you gain is not just the 2 peak Tqm it's the area under the curve, you'll notice that with the MREV2, you gain almost everywhere else, all through the range.
07-17-2012, 04:43 AM
#40
Thanks for your inputs.
I already talked to someone in JWT and I'm just waiting for their engineers to reply.
I'm going to return my mrev2 since they have better power through out. With regards to headworks it might be an options, but I'm still waiting for jwt's engineers inputs. I also might need to increase my compression ratio. or just go for boost (long shot since I'm afraid the car might not be reliable anymore )
I already talked to someone in JWT and I'm just waiting for their engineers to reply.
I'm going to return my mrev2 since they have better power through out. With regards to headworks it might be an options, but I'm still waiting for jwt's engineers inputs. I also might need to increase my compression ratio. or just go for boost (long shot since I'm afraid the car might not be reliable anymore )