pulley with and without tune on a 12

[heatsoaked12]

Honestly I don't think there is a short way of telling these events but I'll do my best. First off I'll say that both the tuners I purchased a tune from are two of the most recommended around here and both were exceptional to talk and deal with. 2015 I purchased a tune to correct my magnum xl gearing and provide a few more ponies. It ran kind of rough with what seemed to be some throttle mitigation rather than more power adding. 2016 from another vendor I purchased a tune and 2.5 pulley. Again a rough and loud engine as though the timing was way up at idle just to give a more responsive tip in of the throttle. With a pulley and tune I expected to be able to rip the tires off the car in first of course (even with the r888 tires )but it wouldn't. 2017 July, I thought, I'm going to try this 2.5 pulley with the stock tune and see how it runs. All else is stock right down to the factory somewhat dirty air filter with the exception being the fanned heat exchanger. Let me tell you, this car is moving like never before, with a smooth idle, smooth power delivery. an iat 2 of 120 to 130 F. One strange thing though, with the pulley staying the same, tuned my boost gage showed boost being at 13 psi and with the factory tune it shows 9 psi. Either way,I've always wondered and see alot of people asking if a tune is needed with a pulley swap. While its only been one evening of testing(wot through many gears ) it seems to be that my car runs stronger and smoother with the 2.5 pulley and factory tune. Have I made a mistake? am I pushing it too far? Let me know what you think. I can tell you this car is hauling ass now. BTW no wrench or warning light as of yet.

 

[Mbiro594]

I contacted Justin over at VMP about running a 2.5 pulley with a 90mm idler without a tune. He said it is not a problem and he had tested it himself back in 2010 and yielded about 20-30whp. 2010+ is ok to do this with as they have a CAI from the factory and a larger MAF.

I am waiting on my tune to arrive but in the meantime was able to have my buddy install the pulley. Definitely an increase!

See email below for reference and peace of mind lol

Also:

Sent from my iPhone using Tapatalk

 

[RedVenom48]

Youll want to revert back to the tune you got and data log. If its not pulling like stock, you were probably given a conservative tune. Once a tuner emails a tune to an owner, its out of his hands what happens. Conservative tune is just a little bit of insurance for the tuner.

A datalog sent back to the tuner can let him see exactly what the car is doing and where he can tweak the tune for max power.

 

[Catmonkey]

Going from a 3" to 2.5" pulley is probably in the range of 5 lb.s of boost, so you are going to pick up more power than a tune with the stock pulley. OEM boost gauge infers boost from MAF output, it's not an accurate means to determine how much boost you're making.

 

[heatsoaked12]

Youll want to revert back to the tune you got and data log. If its not pulling like stock, you were probably given a conservative tune. Once a tuner emails a tune to an owner, its out of his hands what happens. Conservative tune is just a little bit of insurance for the tuner.

A datalog sent back to the tuner can let him see exactly what the car is doing and where he can tweak the tune for max power.

Good info here thanks! I would think a safe tune would still outperform a stock tune. Stock tune with a pulley almost scares me on the street even with the r888 tires.

 

[heatsoaked12]

Going from a 3" to 2.5" pulley is probably in the range of 5 lb.s of boost, so you are going to pick up more power than a tune with the stock pulley. OEM boost gauge infers boost from MAF output, it's not an accurate means to determine how much boost you're making.

Thanks for your input, one would think infered boost would still read higher with a smaller pulley.I may hook up a mechanical boost gage just to see how far off it really is and how accurate the boost gage was with a tune . it always showed full boost at 13 psi.

 

[heatsoaked12]

My next move is a resonator delete. Anyone think I'm pushing the stock maf yet? It will just be with the stock maf and air filter.

 

[RedVenom48]

Honestly, with just a pulley and tune your not pegging the stock intake. Its future POTENTIAL to make power is capped. Factory ignition timing maps, fuel maps etc are all tied to the known intake size, cooling capacity of the stock intercooler system (boost discharge temps), a 180 degree T-stat for the engine cooling system and fuel octane supplied. Size of the throttle body is also taken into account.

A dual fan triple pass heat exchanger, and installation of a 170F degree T-stat will open up the potential in a tune from the likes of Lund and VMP etc. Add a higher flowing Throttle body and off road exhaust and your potential goes up even more. The upgraded 120mm intakes will be adjusted via MAF curve allowing more fueling capacity. Understand, we arent talk earth shattering increases in power, but each mod supports the next. BJ from VMP, Matt from Billet Pro Shops and many members here on this board have taken their M122 powered GT500s into the 10s. Intake, pulley, heat exchangers, t stat, tune, throttle body, in some cases porting the m122, exhaust and suspension and TIRE selection all play a factor.

Spark plugs are another area where you'll have to account for the high boost capable with the smaller pulley. I run, and many here also run, the NGK TR7IX. Its 2 steps colder than the stock plug. Its to help reduce the possibility of the spark plug overheating from the increased power (heat) of the higher boost AF mixture. An overheated spark plug will deteriorate and lead to preignition. In a boosted car like ours, thats almost certain engine damage if not regularly checked. A colder plug will normalize this "wear" on the plug. If gapped properly, a colder range plug like the TR7IX should work with the factory tune.

Honestly though, Id give your tuner a call, send data logs and get that tune working for your car. Factory tune can only take into account so much before it falls outside its parameters. The custom tune will take all this into account and make sure all the mods done to the car are contributing.

Remember though, quality fuel is paramount. The most 91 pump gas can typically handle is 15 psi or so. 93 gives you a little bit more room to play but it tops out I think around 16-17 psi. The 2010-2014 GT500s come with a factory knock sensor setup. Based on the knock detected, it attempts to give the most aggressive spark advance the fuel can support. So a min octane of 91 can be used all the way to 93 with no needed input from the driver.

 

[1Kona_Venom]

^ always enjoy reading his posts

 

[heatsoaked12]

Honestly, with just a pulley and tune your not pegging the stock intake. Its future POTENTIAL to make power is capped. Factory ignition timing maps, fuel maps etc are all tied to the known intake size, cooling capacity of the stock intercooler system (boost discharge temps), a 180 degree T-stat for the engine cooling system and fuel octane supplied. Size of the throttle body is also taken into account.

A dual fan triple pass heat exchanger, and installation of a 170F degree T-stat will open up the potential in a tune from the likes of Lund and VMP etc. Add a higher flowing Throttle body and off road exhaust and your potential goes up even more. The upgraded 120mm intakes will be adjusted via MAF curve allowing more fueling capacity. Understand, we arent talk earth shattering increases in power, but each mod supports the next. BJ from VMP, Matt from Billet Pro Shops and many members here on this board have taken their M122 powered GT500s into the 10s. Intake, pulley, heat exchangers, t stat, tune, throttle body, in some cases porting the m122, exhaust and suspension and TIRE selection all play a factor.

Spark plugs are another area where you'll have to account for the high boost capable with the smaller pulley. I run, and many here also run, the NGK TR7IX. Its 2 steps colder than the stock plug. Its to help reduce the possibility of the spark plug overheating from the increased power (heat) of the higher boost AF mixture. An overheated spark plug will deteriorate and lead to preignition. In a boosted car like ours, thats almost certain engine damage if not regularly checked. A colder plug will normalize this "wear" on the plug. If gapped properly, a colder range plug like the TR7IX should work with the factory tune.

Honestly though, Id give your tuner a call, send data logs and get that tune working for your car. Factory tune can only take into account so much before it falls outside its parameters. The custom tune will take all this into account and make sure all the mods done to the car are contributing.

Remember though, quality fuel is paramount. The most 91 pump gas can typically handle is 15 psi or so. 93 gives you a little bit more room to play but it tops out I think around 16-17 psi. The 2010-2014 GT500s come with a factory knock sensor setup. Based on the knock detected, it attempts to give the most aggressive spark advance the fuel can support. So a min octane of 91 can be used all the way to 93 with no needed input from the driver.

I do have a 170 thermostat and a super competition hx from van. I am still a work in progress, I have never data logged anything in my life but looking to learn more about it. Thanks for your post, its golden.