Modifying ARROW PCM tune possible

[Terminator02]

Im gonna highjack the thread, is it just me or does it seem to be all the gearheads that have modded a gen v have not had a engine failure?. Is there any known. ?. Seems people that know a working engine have no failure rate.no? Besides ralphs.

I think there are a fair number of "at risk" cars that were modded to their owner's liking and been fine. I know a few people not on the forums that have the arrow and a few bolt-ons with 7k+ miles with no issues. Andy knows the stats of his H&C packages but only 1-2 have failed I believe out of maybe 45 cars? I'm not sure about Woodhouse numbers but I haven't heard of one H&C car fail. Again, this is ballpark but maybe 2 out of 60+ have failed which is a far lower % than the average. I think most of the highly modded cars are driven often and well-maintained. There's no guarantee but you can mitigate the risk factors by doing the following:
1. Check oil correctly and often
2. Row the gears!
3. Get a baseline Blackstone analysis and repeat for any trends

Regarding the started thread, I agree with Andy in having trust in Winkles execution decision and make changes with the PCM instead of doing a 180. For everyone that says it's a conservative tune well they are correct. However, outside of a few dyno runs, the 1/4 mile times and actual trap speeds tell a story that the cars are running very very strong with the Winkles ECU. There are awesome tuners out there doing some great things but I am constantly amazed at how streetable my car is with nearly 800 all motor horsepower.

Dave

[Dave1968]

Is there any way to "fool" the IAT sensor to think it's a lot cooler than it is and then load up on 94 octane to make sure there is no detonation ? I can get 94 all day long up here.

[Jack B]

Is there any way to "fool" the IAT sensor to think it's a lot cooler than it is and then load up on 94 octane to make sure there is no detonation ? I can get 94 all day long up here.

The IAT is part of the MAF sensor, that makes it difficult. What you can do is slow down the heat rise by shielding the exposed part of the assembly. You can also add the air box heat shield. These will both help, but, not eliminate the heat rise.

Someone mentioned Ralph's bearing failure, there were reasons other than a defect for the failure.

[Dave1968]

How about something crazy like this. We find out which wires are associated with the IAT part of the sensor array. Usually sensors like this rely on voltage changes to communicate. If we can determine which way it goes (i.e. the higher the temp. the higher the voltage, etc...) then from Ohm's law E=IR we could either add or subtract resistance to "adjust" the reading by say 20 degrees. Therefore at 90 degrees it would think it was 70 and not pull timing - the reading would always be 20 degrees out or so depending on whether it was a linear progression etc... Then make sure you have lots of octane in your fuel and or course pay attention to your car etc. and you wouldn't have to mod the tune in any way. Now I don't know if we could in fact isolate the wires in this way or if the system simply uses the same ones for everything and the computer just knows who is trying to communicate with it at any given time , the tech guys on this forum could probably nail that part down.

[Jack B]

That is how piggybacks work, the Roe Vec 1 and the Vec 2 are examples. Good what-to-do for the winter. What you describe is simple.

How about something crazy like this. We find out which wires are associated with the IAT part of the sensor array. Usually sensors like this rely on voltage changes to communicate. If we can determine which way it goes (i.e. the higher the temp. the higher the voltage, etc...) then from Ohm's law E=IR we could either add or subtract resistance to "adjust" the reading by say 20 degrees. Therefore at 90 degrees it would think it was 70 and not pull timing - the reading would always be 20 degrees out or so depending on whether it was a linear progression etc... Then make sure you have lots of octane in your fuel and or course pay attention to your car etc. and you wouldn't have to mod the tune in any way. Now I don't know if we could in fact isolate the wires in this way or if the system simply uses the same ones for everything and the computer just knows who is trying to communicate with it at any given time , the tech guys on this forum could probably nail that part down.

[Dave1968]

Another thought. The PCM would want an accurate IAT reading for its calculations and this could / would screw it up tuning wise. However, would the affects of the IAT out 20 or so degrees be worse than the affects of all the pulled timing?

[Jack B]

One of the biggest issues is when the car heat soaks, such as in the staging line at the dragstrip. The true air temp might be 75 degrees, however, the IAT sensor shows 100 degrees due to heat soak of the air tubes and IAT housing. I would call this a false reading, however, it still robs power. This might be the application for a variable resistor in the analog IAT circuit. The resistor will probably have to be in parallel with the IAT.

A second issue is the differential between true air temp and IAT reading when the car is moving. I think at 70 mph a stock car sees a differential of approx 20-25 degrees in a 75 degree ambient. I have measured the true IAT when the car is moving and it is lower than the sensor value. If you use an airbox deflector plate and some insulation on the airbox and tubes, you can get it down to approx 10 degrees. This will help the road racers and roll racers. This again is sort of a false reading, the IAT sensor is not seeing true air temps, the external part of the sensor is being heated by external conducted heat, convected heat and radiated heat

Lastly, as the pcm pulls timing it typically adds fuel, the car then goes super rich, that is why you lose so much power. You are correct, if you have a true 90 degree day and you are road racing, most of this is a bad idea.

Another thought. The PCM would want an accurate IAT reading for its calcula.tions and this could / would screw it up tuning wise. However, would the affects of the IAT out 20 or so degrees be worse than the affects of all the pulled timing?

[Dave1968]

I see what you mean. My idea is centered around simple street driving and playing around, not drag racing. It just seems like pretty much all the time the car is going to be under powered because of this annoying reaction to the IAT. 70 degrees, 21 cel. is way too low of a threshold I think. I would like to explore this a little further to see if it would be feasible. It would be very easy to wire in a switch so that one could revert back to stock configuration if it did get very hot or even just for normal driving. Kind of like switching on and off Nitrous.

[dethred]

I guess no one knows for sure whether or not this is possible, and I am not going to dump another $1000 into this car on a hunch, when I should have gone with HP Tuners in the first place. Oh well. If anyone has both and is willing to try, that would be awesome!

To be honest, advertising "640 horsepower" when the baseline OE tune makes less than that any time between April and October in most of the country, is fairly misleading. Not to mention, if an unmodified car is pulling in <77*F air, then the ambient temperatures will be in the 50's or low 60's, which is far too cold to actually put the power down.

[camarochevy1970]

So I answered this when you asked in a different thread, and Steve M answered it in this one

I'll clarify what has already been stated...you do not want to overwrite your Arrow PCM with HPTuners. It isn't that it won't work, it's that you'll overwrite their calibration.

So you can probably tune an Arrow controller with HP Tuners, but you have to dispose of the Arrow calibration to do it, that's just how it works on Gen 5's

[Jack B]

The pcm may start pulling timing down near 70 degree, however, it is not noticeable till the IAt gets in the 90's. Very little timing is pulled below 90 degrees.

I see what you mean. My idea is centered around simple street driving and playing around, not drag racing. It just seems like pretty much all the time the car is going to be under powered because of this annoying reaction to the IAT. 70 degrees, 21 cel. is way too low of a threshold I think. I would like to explore this a little further to see if it would be feasible. It would be very easy to wire in a switch so that one could revert back to stock configuration if it did get very hot or even just for normal driving. Kind of like switching on and off Nitrous.

[Dave1968]

Thankyou, that's good to know. I see you have tuned your own car; do you happen to know how much is pulled and when, or where I can get this info. - either by numbers or graph?

[Steve M]

This is the table you are looking for:



The PCM does a linear interpolation between those points, so it doesn't pull any timing at 77°F, but beyond that it starts ramping up - 1° pulled at 80°F, 2° pulled at 83°F, and so on.

[uberpube]

Is there any way to "fool" the IAT sensor to think it's a lot cooler than it is and then load up on 94 octane to make sure there is no detonation ? I can get 94 all day long up here.

When you say "up here", do you mean Canada? Are you talking about husky/mohawk/petro-can 94? That fuel might have a 94 octane rating but its loaded with ethanol to get the octane rating, and if the fuel is older, or wet the alcohol likes to absorb water which means a lower octane. Also there is an SAE paper about mixed fuels that found that two fuels don't remain totally mixed during vaporization and the alcohol can cause knock when that happens. . . My experience with the 94 from tuning my RX-7 to the limit on pump gas, is that pure gasoline with a lower octane rating will allow more timing and power than the ethanol loaded 94. I was at 480 on 94 when knock started to show up and dropping it a full point on AFRS's didn't help it. I made a reliable 502 rwhp on 91 octane with no knock present with a hot intercooler. The car was probably making more than that when out on the road with intercooler airflow.... I'd stay away from the 94.

[dethred]

So I answered this when you asked in a different thread, and Steve M answered it in this one



So you can probably tune an Arrow controller with HP Tuners, but you have to dispose of the Arrow calibration to do it, that's just how it works on Gen 5's

So you've tried it I assume? It just seems strange that an oem PCM can be tuned with HPtuners, but with an arrow calibration on it, it'll somehow wipe it out back to Oem.

Steve M is showing the timing tables but I don't know if that's indicating they're available to be modified on the ARROW PCM.

[camarochevy1970]

So you've tried it I assume? It just seems strange that an oem PCM can be tuned with HPtuners, but with an arrow calibration on it, it'll somehow wipe it out back to Oem.

Steve M is showing the timing tables but I don't know if that's indicating they're available to be modified on the ARROW PCM.

I know how HP tuners works on the gen 5. It doesnt read the existing calibration it builds a new oem calibration based off your car details. So if you read an arrow controller it is going to give you a stock file with your vin and car data and overwrite anything existing on the ecm if you save it back

[dethred]

I know how HP tuners works on the gen 5. It doesnt read the existing calibration it builds a new oem calibration based off your car details. So if you read an arrow controller it is going to give you a stock file with your vin and car data and overwrite anything existing on the ecm if you save it back

Thanks, that was the info I was looking for. I thought the tuner would obtain the tune on the PCM as it is, and allow you to modify it. Damn...

[Dave1968]

When you say "up here", do you mean Canada? Are you talking about husky/mohawk/petro-can 94? That fuel might have a 94 octane rating but its loaded with ethanol to get the octane rating, and if the fuel is older, or wet the alcohol likes to absorb water which means a lower octane. Also there is an SAE paper about mixed fuels that found that two fuels don't remain totally mixed during vaporization and the alcohol can cause knock when that happens. . . My experience with the 94 from tuning my RX-7 to the limit on pump gas, is that pure gasoline with a lower octane rating will allow more timing and power than the ethanol loaded 94. I was at 480 on 94 when knock started to show up and dropping it a full point on AFRS's didn't help it. I made a reliable 502 rwhp on 91 octane with no knock present with a hot intercooler. The car was probably making more than that when out on the road with intercooler airflow.... I'd stay away from the 94.

I see what you mean. I have done some research on the whole ethanol thing and yes, in some circumstances with old fuel you may have separation of the alcohol from the gasoline, but I don't think I'm experiencing that. The places I go for fuel are very busy and hopefully their stock is current - appears to be. My other method has been to use Shell premium ( 0 ethanol) and add Amsoil Dominator octane boost.