Voltage question for dyno
Thread Starter
Melting Slicks
Joined: Nov 2000
Posts: 2,469
Likes: 6
From: Winchester Ontario
Voltage question for dyno
***EDIT***
This was on a DTS engine dyno. Not sure of model #
***EDIT***
I was breaking in / dynoing my engine at the start of the week. We started at base 0 degrees (oops LOL) and put some fuel to it so we knew we were safe. We kept increasing timing (to like 16 deg or so) and made a peak of 480 hp and 506 tq.
We increased the timing again and power started falling off so we backed the timing back up but couldn't get the power back. There were many inconsistencies with the dyno. Had many runs with 500 + tq but the top end was seeming to fall off.
Peak hp was like 5400 rpm and tq was 4400.
My actual question is... Since we were using a battery pack, is there a chance that since the voltage was dropping, the msd wasn't receiving enough volts to keep up at the top end?
Near the end , we were getting like 12.3 at idle / start of dyno and dropping to high 11.9's near the end. Would the low voltage affect the power output if it can't supply the ignition box/coil with enough juice?
383 @ 10:1
230/230 @ 0.050 , 0.598" lift with 1.6 rr's
AFR 195 Eliminators
Edelbrock RPM Air Gap
Pro Systems Racing carb 830 cfm
MSD #8360 distributor
MSD 6AL-2
MSD Coil #8207
This was on a DTS engine dyno. Not sure of model #
***EDIT***
I was breaking in / dynoing my engine at the start of the week. We started at base 0 degrees (oops LOL) and put some fuel to it so we knew we were safe. We kept increasing timing (to like 16 deg or so) and made a peak of 480 hp and 506 tq.
We increased the timing again and power started falling off so we backed the timing back up but couldn't get the power back. There were many inconsistencies with the dyno. Had many runs with 500 + tq but the top end was seeming to fall off.
Peak hp was like 5400 rpm and tq was 4400.
My actual question is... Since we were using a battery pack, is there a chance that since the voltage was dropping, the msd wasn't receiving enough volts to keep up at the top end?
Near the end , we were getting like 12.3 at idle / start of dyno and dropping to high 11.9's near the end. Would the low voltage affect the power output if it can't supply the ignition box/coil with enough juice?
383 @ 10:1
230/230 @ 0.050 , 0.598" lift with 1.6 rr's
AFR 195 Eliminators
Edelbrock RPM Air Gap
Pro Systems Racing carb 830 cfm
MSD #8360 distributor
MSD 6AL-2
MSD Coil #8207
Last edited by black_89_vette; Jul 26, 2013 at 07:54 AM.
Thread Starter
Melting Slicks
Joined: Nov 2000
Posts: 2,469
Likes: 6
From: Winchester Ontario
Due to the consistency problems, we quit the Mon night and decided that Tues would start over in the morning with cold air temps cuz Mon was hot and humid.
The first run of the day was 534 hp and 571 tq which seemed too high on tq for sure but 1 min later it was like 466 hp and 485 tq or so. Maybe the first run had enough juice in the battery pack and it drained it for that run and each run was low thereafter (we did plug in the battery pack at this point but it never charged very high.
The first run of the day was 534 hp and 571 tq which seemed too high on tq for sure but 1 min later it was like 466 hp and 485 tq or so. Maybe the first run had enough juice in the battery pack and it drained it for that run and each run was low thereafter (we did plug in the battery pack at this point but it never charged very high.
Melting Slicks
Joined: Jun 2013
Posts: 3,065
Likes: 39
Yes it would. Most definitely. Lesser voltage means a colder spark with leads to less fuel burned. Check to see if your serpentine belt is slipping. Look on your pullies and see if the paint is shaved off them in a few places. Your voltage on a healthy alternator should stay between 13.5 -14.5 volts when running at all times.
Thread Starter
Melting Slicks
Joined: Nov 2000
Posts: 2,469
Likes: 6
From: Winchester Ontario
Thanks for the reply. Due to not wanting the power steering fluid pumping all over and burning out the pump (and we didn't make it a closed system for the dyno), we bypassed the power steering pump and alternator when we routed the belt. This is why we used the battery pack for the engine dyno.
I was wondering about the voltages in the battery pack dropping and thought it would cause the power output to drop as well.
Oh, by the way, I was using an MSD 6AL-2, MSD 8360 distributor and an MSD Blaster SS Coil # 8207.
I was wondering about the voltages in the battery pack dropping and thought it would cause the power output to drop as well.
Oh, by the way, I was using an MSD 6AL-2, MSD 8360 distributor and an MSD Blaster SS Coil # 8207.
Thread Starter
Melting Slicks
Joined: Nov 2000
Posts: 2,469
Likes: 6
From: Winchester Ontario
Hmm, low voltage= colder spark leading to less fuel burned.
To bring some power back up , we jetted the carb higher and ran it pig rich (11.9 - 12.3 or so) readings came from wb 02 sensors on headers that we were using.
To bring some power back up , we jetted the carb higher and ran it pig rich (11.9 - 12.3 or so) readings came from wb 02 sensors on headers that we were using.
Safety Car
Joined: Sep 2001
Posts: 4,157
Likes: 554
From: Glenbeulah Wi
I doubt 11.9 volts is too low to run an MSD ignition system. Many race cars (Drag cars) do not run an alternator and they run fine with voltage in the 11's on the run. If you were misfiring a plug the WB would start to read very lean at the end of the run due to all the oxygen in the exhaust that was not burned. What were the WB reading like at the end of the run? What was your total timing at the WOT, you list the base but not the total. It sounds to me like you may have some detonation issues (Too much timing), heat soak issue, or incorrect WOT AFR to loss that much power on the dyno between a cold run and a warm run.
Thread Starter
Melting Slicks
Joined: Nov 2000
Posts: 2,469
Likes: 6
From: Winchester Ontario
We changed timing many times throughout the runs, but I think it liked 16 deg base and like 38 total if I recall. We even got it up to 19 base and total of 41.
Throughout the course of the dyno runs, it did lean out to 13.4 ish and losing power, so we rejetted (76/86 to 80/89) and added more timing which started to bring the numbers back. When we rejetted the carb, we were getting high 11's and low 12's on the AFR which is pig rich but made more power than the lean runs.
It was very frustrating , we were taking out timing and adding timing and the numbers were erratic which led me to think it was an issue with the dyno or battery pack.
The temps were ok during the runs, we let it cool down if it got high, so no heat soak issues I don't believe.
We checked the plugs and they looked ok. We also did a compression check and 6 of the 8 were 175 and the other 2 were 180.
Throughout the course of the dyno runs, it did lean out to 13.4 ish and losing power, so we rejetted (76/86 to 80/89) and added more timing which started to bring the numbers back. When we rejetted the carb, we were getting high 11's and low 12's on the AFR which is pig rich but made more power than the lean runs.
It was very frustrating , we were taking out timing and adding timing and the numbers were erratic which led me to think it was an issue with the dyno or battery pack.
The temps were ok during the runs, we let it cool down if it got high, so no heat soak issues I don't believe.
We checked the plugs and they looked ok. We also did a compression check and 6 of the 8 were 175 and the other 2 were 180.
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