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Old 10-24-2010, 01:37 PM   #1
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Jeep wrangler dyno results (Air temp experiment)

Purpose
These tests were done to determine the effect of higher air intake temps (ACT, air charge temp) on hp output. The torque is missing from the data because it was difficult to get a good rpm signal. (the coil pack is enclosed so you can't tap just one coil) I used the optical sensor on the dampener and it would sometimes loose the signal due to engine movement. This is why all the pulls are based on mph of the dyno drum instead of rpms.

Results






This is the data for all 4 pulls. You can see each pull by the increase in rpm. Notice the drastic increase in ACT. Part of this may be due to radiator wash increasing the ACTs, but that would be very typical in a slow moving, rock crawling jeep.




Here you can see that the jeep goes open loop in an attempt to richen the mixture and decrease combustion temps at the expense of hp.



Conclusion
Holy crap!! A loss of 73.54 hp is no joke!! I never expected anything as drastic as this. In 4 minutes the power went down 56%! Time to install the cowl air intake and retest.

Notes
It seems that the jeep runs closed loop at WOT until the temps reach a certain point. This was clearly visible on the last 2 runs while line graphing the commanded AFR, and the jeep ran closed loop on the first 2 pulls. MAP remained nearly identical for all runs. I am not sure if I was logging the correct values for spark timing because there was only a 3* difference between the highest and lowest hp pulls. (this was my first time logging with diablo hardware) Maybe the jeep is that sensitive to a few degrees of timing and a richer AFR. More tests and research will be needed to figure this out.

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Old 10-24-2010, 02:39 PM   #2
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interesting. do the Windstar coil intake box and report back. I've noticed the huge power decrease with air temp, and i've noticed my Scangauge showing open loop vs closed loop. it will hit open loop about 2700-3000rpms on the highway with intake temps around 150 F. i've got a Unichip, and when its turned on, it will trip a misfire code once it hits open loop...even with 93 octane at 11,000 ft. the 4.0L doesn't have a knock sensor...so not sure how the PCM decides when there is a misfire...do you know? programmed tables maybe? something through the coil packs? and wow, A/F ratio is all over the place stock....yuck

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Old 10-24-2010, 03:42 PM   #3
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Originally Posted by UnlimitedLJ04 View Post
interesting. do the Windstar coil intake box and report back. I've noticed the huge power decrease with air temp, and i've noticed my Scangauge showing open loop vs closed loop. it will hit open loop about 2700-3000rpms on the highway with intake temps around 150 F. i've got a Unichip, and when its turned on, it will trip a misfire code once it hits open loop...even with 93 octane at 11,000 ft. the 4.0L doesn't have a knock sensor...so not sure how the PCM decides when there is a misfire...do you know? programmed tables maybe? something through the coil packs? and wow, A/F ratio is all over the place stock....yuck
Misfire codes are detected when the acceleration of the crank shaft slows a bit (when a cylinder doesn't fire). The AFR is not all over the place. Its about 14.7 most of the time until the ecu richens it up for high temps.
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Old 10-24-2010, 04:13 PM   #4
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A 25 degree increase in incoming air loses 73 horsepower?

Where was the air temp taken - right at the TB?

Was this using the stock airbox? If so, no compensation was done for the restriction of the ducting, airbox, and that tiny airhorn all the air has to pass through.

Try just taking that little funnel off and see what a difference it makes.

Then try it with the TB open to atmosphere - nothing attached to it, letting underhood temps take affect but eliminating the ducting/filter restrictions.

That will give you a base to compare from.
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Old 10-24-2010, 05:03 PM   #5
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Stock type filter with the stock air box with the horn. On another day i will do more tests including what you mentioned. First i will do back to back pulls with the hood open and dyno fans running to make sure it is repeatable. Then i will remove the horn, then the filter, then the intake itself. Then i'll try the same tests with the hood closed and dyno fans off. But don't hold your breath because i have real customers lined up for tuning on top of my regular day job. And them my first kid is due next week!
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Old 10-24-2010, 06:07 PM   #6
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Your temps you show:
124F = 51C 131hp
149F = 65C 57.7 hp

According to: www.gadgetjq.com/ping_mod_resistance-fueladd.xls

At 51 C the air density is .05887
At 65C the air density is .05402

That's a difference of 8.2% -

So the higher temperature will have only 8% LESS oxygen in it. The computer using the O2 sensor will detect there's not quite enough oxygen, so it'll cut back the amount of fuel appropriately to maintain it's pre-programmed Air to Fuel ratio, approximately at Stochiometric of 14.7 : 1.
.
At MOST I would think there could be a loss of 8.2% of the horsepower at the hotter temperature due to the temperature change.

One thing that may throw things off too - I think the computer is programmed to drop out of closed loop and go richer intentionally at WOT. It may not be instantaneous, there may be a delay before it drops out.

I strongly suspect the loss of HP is really due to the restriction factor at the higher speeds. At lower speeds enough air flows - leading to the rumors it's “adequate.” But the faster the engine turns, the more air it needs - and the restrictive stock box system restricts it.

When I had my performance dyno shops I did a little experimenting with inlet temperatures - I found it did make a difference, but the difference was very minor compared to eliminating restrictions to the airflow (in and out.) But - I did not have the benefit of the computerized software like you do. Data collection was mainly notes taken on the fly. Crude at best.

I love the fact you are actually doing it - you will be able throw lots of light on the subject - and disavow lots of “seat of the pants rumors.”

Keep up the good work!

.
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Old 10-25-2010, 10:31 AM   #7
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At 51 C the air density is .05887
At 65C the air density is .05402

That's a difference of 8.2% -

So the higher temperature will have only 8% LESS oxygen in it. The computer using the O2 sensor will detect there's not quite enough oxygen, so it'll cut back the amount of fuel appropriately to maintain it's pre-programmed Air to Fuel ratio, approximately at Stochiometric of 14.7 : 1.
.
At MOST I would think there could be a loss of 8.2% of the horsepower at the hotter temperature due to the temperature change.
I will have to review the code, but from the data collection on the stock tune the jeep will normally run closed loop at WOT (14.7). The ECU will automatically adjust for the "missing" O2 for the higher temps, but that is not the source of the severe loss of power. When the ACT goes up the engine will be more prone to knocking and the ecu will do things to make sure that doesn't happen, like richen up the mixture, and retard the timing. One thing that popped into my mind is the fan. I'm sure all of you know the fan sucks a ton of hp out of the jeep and it feels real slow when its on. I'll have to review the datalog to see if i logged the fan status and if that was a contributor. There has to be something i'm missing if its not the fan because a couple degrees of timing and a rich mixture is NOT going to cause a >50% drop in power output.
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Old 10-25-2010, 11:01 AM   #8
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I'm gonna call BS on your test. 73HP drop. sorry but no.

you need more pulls at each degree. something went wonky on that last pull. unless you really believe 57hp. Your AF ratio is shit on last 2 runs as well. When running WOT, the ECU keeps 14.7...or as close to it. so there's something you're not telling us.

compare runs 6 and 7...those look like the only 2 worth looking at. 40 HP change is depressing on its own right. But I must ask, were you running fans? If not then the results are poor, as, if you were going these speeds your jeep would have air blowing past it...unless you live in a vaccum.

I could see a 15hp loss on the fan alone. but this is pure speculation. I'd be more interested in a test of E fan vs clutch fan....rather than "cowl intake". as the location of the intake isn't the issue. the heatsoak is occuring to the intake tract, which cannot be avoided at a maintainable amount...unless you add alcohol injection. but I don't think that's something worth doing on a Jeep.

try open TB, see if it gains anything. I doubt it will gain an impressive amount, however you can make it gain whatever you like by doing whatever you did on the last couple of runs.

what were you using for A/F readings? and where was it placed? needs to be before cat for most reliable results. and should be a wideband aftermarket sensor.
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Old 10-25-2010, 11:30 AM   #9
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Originally Posted by mrcarcrazy View Post
I'm gonna call BS on your test. 73HP drop. sorry but no.

you need more pulls at each degree. something went wonky on that last pull. unless you really believe 57hp. Your AF ratio is shit on last 2 runs as well. When running WOT, the ECU keeps 14.7...or as close to it. so there's something you're not telling us.

compare runs 6 and 7...those look like the only 2 worth looking at. 40 HP change is depressing on its own right. But I must ask, were you running fans? If not then the results are poor, as, if you were going these speeds your jeep would have air blowing past it...unless you live in a vaccum.

I could see a 15hp loss on the fan alone. but this is pure speculation. I'd be more interested in a test of E fan vs clutch fan....rather than "cowl intake". as the location of the intake isn't the issue. the heatsoak is occuring to the intake tract, which cannot be avoided at a maintainable amount...unless you add alcohol injection. but I don't think that's something worth doing on a Jeep.

try open TB, see if it gains anything. I doubt it will gain an impressive amount, however you can make it gain whatever you like by doing whatever you did on the last couple of runs.

what were you using for A/F readings? and where was it placed? needs to be before cat for most reliable results. and should be a wideband aftermarket sensor.
Call BS all you want, but there was no trickery going on here. I'm as surprised as you and I would have bet $100s that there wouldn't even be a 40hp drop in 4 pulls. Here is the datalog and you can review it yourself.
http://www.tricktuners.com/forums/at...5&d=1288016914
you will need to download the free diablo dataviewer software to open it.

As already stated there were no radiator fans running and the hood was closed. I was running my 18,000cfm exhaust fan that clears the room over 4x a min so there is no issue about sucking in any exhaust. The AFR was read from the tail pipe with the DJ sniffer and a sensor with only about 10 pulls on it. You can see the commanded AFR in the datalogs where the ecu richenes up the mixture only on the last 2 pulls and it correlates well with the data that was collected off the dyno. I'll gladly post up the drf files if you want to review them yourself.
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Old 10-25-2010, 12:57 PM   #10
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well then your Jeep is broken.

the 73HP drop is faulty, I don't know why(as in the cause), but I can say that it is. the 40HP drop is shocking on its own right. I am purely stating that the 73HP drop is more likely due to another factor than heat....

Running no fans is poor technique....If you're trying to be accurate at least.

I don't like Tailpipe sniffers, but I don't think yours is faulty, I just don't think they are as accurate...but this is based off of now old knowledge, so I could be off by today's standards.

I'd be mostly curious to find out why your Jeep found it necessary to dump fuel...(and I'm ignoring the last pull, as I'm convinced something is up with that one)

I'm merely stating that your conclusion is faulty...its not logical. something else is going on. I am not saying you are a liar, just that there is something "up" with your test. It will take someone more knowledable than myself to figure out what, but it doesn't mesh well...and that's usually a sign that somebody did something wrong.
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Old 10-25-2010, 02:57 PM   #11
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well then your Jeep is broken.

the 73HP drop is faulty, I don't know why(as in the cause), but I can say that it is. the 40HP drop is shocking on its own right. I am purely stating that the 73HP drop is more likely due to another factor than heat....

Running no fans is poor technique....If you're trying to be accurate at least.
That was the purpose of the test. To show the effect of hot under hood temps. I would never attempt to tune a car without both my 4' fan, and the smaller hurricane fan, both pointed at the radiator with the hood open. These are the fans that i use for every other pull.



Quote:
Originally Posted by mrcarcrazy View Post
I don't like Tailpipe sniffers, but I don't think yours is faulty, I just don't think they are as accurate...but this is based off of now old knowledge, so I could be off by today's standards.
Sniffers are not as accurate, but they are still very precise. The accuracy is typically biased about 0.1 to 0.2 AFR units leaner than when measured pre-cat. I don't tune high powered cars with the sniffer and i will install dual WO2s precat. For this test, its just fine.
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Originally Posted by mrcarcrazy View Post
I'd be mostly curious to find out why your Jeep found it necessary to dump fuel...(and I'm ignoring the last pull, as I'm convinced something is up with that one)
Dumping fuel is a VERY common way to reduce temps. Sometimes oem calibrations will specify 10:1 AFR ratios for things like catalytic converter high temp, high ECT, and high ACT.
Quote:
Originally Posted by mrcarcrazy View Post
I'm merely stating that your conclusion is faulty...its not logical. something else is going on. I am not saying you are a liar, just that there is something "up" with your test. It will take someone more knowledable than myself to figure out what, but it doesn't mesh well...and that's usually a sign that somebody did something wrong.
You must have missed this. I never said that the loss of hp was strictly due to high intake temps.
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There has to be something i'm missing if its not the fan because a couple degrees of timing and a rich mixture is NOT going to cause a >50% drop in power output.
On one of my future tests i will turn the fan on to rule that in or out, but my gut feeling says the fan was a much bigger player in the hp losses than the higher temps.
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Old 10-25-2010, 03:26 PM   #12
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This is very interesting I'm going to be following up. This could solve the problem of a lack of power that some people complain of and try to fix with CAI exhaust and other things that will ad like 3 or 4 hp to the wheels. Thanks for posting this up.
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Old 10-25-2010, 08:14 PM   #13
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Not rocket science - run it in closed loop - monitor it with a scanner or the like.
Twist the TPS to the WOT throttle position (remove it from the shaft, or connect a dummy TPS to the connector - notice it drops out of closed loop - that makes it go richer - like your tests found.

The method used to be a separate WOT contact to tell the computer (GM, Ford etc) - now they just monitor the TPS position.

You can do it under load or even unloaded. If it doesn't the TPS isn't moving far enough.
The reasoning is to gain a tad more power temporarily and to keep things cooler, avoiding ping.

But - the HP loss is not from the temp of the incoming air, it's the restrictive air inlet.
Look at your charts, it's easy to see it's getting "CHOKED."

Running it without any ducting or restriction in the intake air path - open TB - will give you the baseline to compare FROM. Monitor the incoming air temp too.

Hood open during that baseline run will be mostly ambient air temp. You can do it again hood closed for warmer air to see if there's much difference, probably very little difference if any. Also monitor incoming air temp, then compare.

Then do all the ducting to bring in cooler air you want to prove or disprove temp makes a big difference. I think you'll find the ducting is more of a detriment than the slight lower temp is an asset.

All the hoopla about the power increase with CAI is not the temp, it's the elimination of the very restrictive air box and ducting - remember - that airbox system is not just for filtration of dirt - it also is put there as a muffler to lower noise - Fed rules. Notice the aftermarkets all increase the noise levels.
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Old 10-26-2010, 01:46 AM   #14
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Quote:
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Was this using the stock airbox? If so, no compensation was done for the restriction of the ducting, airbox, and that tiny airhorn all the air has to pass through.

Try just taking that little funnel off and see what a difference it makes.
I can tell you how much power you'll gain by removing the airhorn from the stock airbox: none. Jp magazine did this test on a dyno and were forced to admit that it made no difference whatsoever--despite the fact that for years they claimed it would make a difference.
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Old 10-26-2010, 09:45 AM   #15
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Quote:
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Not rocket science - run it in closed loop - monitor it with a scanner or the like.
Twist the TPS to the WOT throttle position (remove it from the shaft, or connect a dummy TPS to the connector - notice it drops out of closed loop - that makes it go richer - like your tests found.

The method used to be a separate WOT contact to tell the computer (GM, Ford etc) - now they just monitor the TPS position.

You can do it under load or even unloaded. If it doesn't the TPS isn't moving far enough.
The reasoning is to gain a tad more power temporarily and to keep things cooler, avoiding ping.
Under normal conditions it looks like the jeep will not go open loop unless the temps reach a certain point, as evident in the first 2 pulls vs the last 2 pulls. I will review the code to determine if this was biased by some sort of startup timer.
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But - the HP loss is not from the temp of the incoming air, it's the restrictive air inlet.
Look at your charts, it's easy to see it's getting "CHOKED."
Sorry, but this theory does not apply to this experiment. If this were true, all the pulls would have the same power output. Why would the intake get "choked" more and more with each pull?
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Old 10-26-2010, 10:24 AM   #16
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Maybe the engine started pinging because of higher temperature?
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Old 10-26-2010, 06:01 PM   #17
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All your pulls show the choke effect - you can see the roll-off.
The ones where you let it drop out of closed loop aren't valid to compare to closed loop.

Try it in open loop vs temp.
Now try it in closed loop vs temp.

Make baseline runs for both ways to compare them to.

Then do your cold air ducting.

Comparing Apples to Burritos isn't valid.
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Old 10-27-2010, 09:55 AM   #18
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Quote:
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All your pulls show the choke effect - you can see the roll-off.
Maybe you can explain this "choke effect" for us.
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The ones where you let it drop out of closed loop aren't valid to compare to closed loop.
I didn't let it do anything on these pulls. It's the stock tune doing what it does. You can clearly see that it didn't go open loop before 4373 rpms on the 3rd pull, and 3907 rpms on the 4th pull. It was still WAY down on power before it went open loop on both of those pulls.
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Old 10-27-2010, 12:14 PM   #19
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Choke effect - stuff a rag in your mouth, then go jogging. ]Or try breathing through that small airhorn on the box. You need far less air than the engine does, so if it's not causing a restriction it won't bother you at all.

The roll-off - all your graphs show it - the power DECREASES above where it's getting restricted. It restricts all the time, but at the higher volume of air it becomes a limit.

You pick your data point AFTER it rolls off.

But OK, you don't want to try it without the restrictive air box - it would certainly go against the thinking on here that the stock airbox doesn't restrict.

Go ahead, prove your point.
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Old 10-27-2010, 01:14 PM   #20
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How would that change with back to back pulls? I understand that the intake may be a restriction, but that would affect all 4 pulls exactly the same, and not decrease power with each successive pull. I will do intake restriction tests some time in the future.
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Old 10-27-2010, 06:38 PM   #21
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I'm very interested in this, it may explain why my Jeep runs like crap when it is super hot out. I know little about running a dyno so I can't give my opinion on your results. I don't know if you have an FSM but you may find this useful, taken from the PCM Chapter of the FSM:
Quote:
WIDE OPEN THROTTLE MODE
This is an Open Loop mode. During wide open
throttle operation, the PCM receives the following
inputs.
- Battery voltage
- Crankshaft position sensor
- Engine coolant temperature sensor
- Intake manifold air temperature sensor
- Manifold absolute pressure (MAP) sensor
- Throttle position sensor (TPS)
- Camshaft position sensor signal (in the distributor)
During wide open throttle conditions, the following
occurs:
- Voltage is applied to the fuel injectors with the
ASD relay via the PCM. The PCM will then control
the injection sequence and injector pulse width by
turning the ground circuit to each individual injector
on and off. The PCM ignores the oxygen sensor input
signal and provides a predetermined amount of additional
fuel. This is done by adjusting injector pulse
width.
- The PCM adjusts ignition timing by turning the
ground path to the coil on and off.
- The Up-shift Indicator Lamp is operated (manual
transmission only).
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Old 10-27-2010, 08:31 PM   #22
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I'm very interested in this, it may explain why my Jeep runs like crap when it is super hot out. I know little about running a dyno so I can't give my opinion on your results. I don't know if you have an FSM but you may find this useful, taken from the PCM Chapter of the FSM:
Thanks. I guess I should have spotted that from the lack o2 switching during the pulls, but I just figured it was closed loop due to the 14.7 afr. Its funny that it runs open loop at stoich unless its hot.
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Old 10-27-2010, 09:17 PM   #23
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I have a crapload more on close/open loop conditions, let me know if you want anything specific
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Old 10-28-2010, 10:04 AM   #24
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Thanks for the offer, but I know a fair bit already. Open and Closed loop Fueling and Fuel Trims - Trick Tuners Forums
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Old 11-08-2010, 10:51 AM   #25
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The above data is incorrect. A problem with the dyno brake was causing it to ride and decrease the numbers on each successive pull. It did seem extremely excessive!! The above experiment will be repeated now that the dyno is fixed.
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Old 11-08-2010, 03:57 PM   #26
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There is the rub! Keep us updated, I'm very interested

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