Fuel Economy with a GTM TT kit!!!

Nixlimited · 07-13-2011, 09:51 AM

Are these calculations based on the on-board computer, or based on actual fuel-usage figures (e.g. fill up and record mileage and gas usage)? I can see a scenario where the on-board computer would miscalculate gas mileage on the high-end. For example, if the on-board ECU used injector pulse length to calculate fuel use, but you had larger injectors, then when cruising the injector pulse would be shorter because the injector is larger, but you are probably using the same or more gas. I just have a very hard time believing that a TT sports car is rivaling hybrid gas mileage on the freeway.

Billy02987 · 07-13-2011, 10:12 AM

Quote:

Originally Posted by Nixlimited

Are these calculations based on the on-board computer, or based on actual fuel-usage figures (e.g. fill up and record mileage and gas usage)? I can see a scenario where the on-board computer would miscalculate gas mileage on the high-end. For example, if the on-board ECU used injector pulse length to calculate fuel use, but you had larger injectors, then when cruising the injector pulse would be shorter because the injector is larger, but you are probably using the same or more gas. I just have a very hard time believing that a TT sports car is rivaling hybrid gas mileage on the freeway.

I believe it does it exactly that way. I've watched my fuel closely since adding my turbos and it definitely hasn't increased even though the on board computer says different. The larger injectors trick it. I drive mostly highways and am pretty conservative and I normally get 300 miles to the tank now. Here's an example of my gas mileage according to the car. I keep telling people I have a hybrid lol. The last picture is what I was getting before the turbos.

ChrisSlicks · 07-13-2011, 10:25 AM

Quote:

Originally Posted by Nixlimited

Are these calculations based on the on-board computer, or based on actual fuel-usage figures (e.g. fill up and record mileage and gas usage)? I can see a scenario where the on-board computer would miscalculate gas mileage on the high-end. For example, if the on-board ECU used injector pulse length to calculate fuel use, but you had larger injectors, then when cruising the injector pulse would be shorter because the injector is larger, but you are probably using the same or more gas. I just have a very hard time believing that a TT sports car is rivaling hybrid gas mileage on the freeway.

Quote:

Originally Posted by Billy02987

I believe it does it exactly that way. I've watched my fuel closely since adding my turbos and it definitely hasn't increased even though the on board computer says different. The larger injectors trick it. I drive mostly highways and am pretty conservative and I normally get 300 miles to the tank now. Here's an example of my gas mileage according to the car. I keep telling people I have a hybrid lol.

Exactly this. The trip computer is estimating fuel economy based on "stock" injector pulse width, the trip computer numbers are meaningless.

Fill to fill measuring the number of gallon you put in the tank by the number of miles driven is the only accurate measurement.

Mr.Squeeze · 07-13-2011, 11:18 AM

Quote:

Originally Posted by Nixlimited

Are these calculations based on the on-board computer, or based on actual fuel-usage figures (e.g. fill up and record mileage and gas usage)? I can see a scenario where the on-board computer would miscalculate gas mileage on the high-end. For example, if the on-board ECU used injector pulse length to calculate fuel use, but you had larger injectors, then when cruising the injector pulse would be shorter because the injector is larger, but you are probably using the same or more gas. I just have a very hard time believing that a TT sports car is rivaling hybrid gas mileage on the freeway.

You are 100 % correct the bigger injectors trick the stock ECU.

Kirkster · 07-13-2011, 11:36 AM

Quote:

Originally Posted by Mr.Squeeze

You are 100 % correct the bigger injectors trick the stock ECU.

Yep. Now we just need to figure out how to fix that...

07-13-2011, 09:51 AM	#1 (permalink)
Nixlimited A True Z Fanatic Join Date: Aug 2009 Location: San Diego Posts: 1,235 Drives: 15 GT-R / 11 Prius Rep Power: 26	Are these calculations based on the on-board computer, or based on actual fuel-usage figures (e.g. fill up and record mileage and gas usage)? I can see a scenario where the on-board computer would miscalculate gas mileage on the high-end. For example, if the on-board ECU used injector pulse length to calculate fuel use, but you had larger injectors, then when cruising the injector pulse would be shorter because the injector is larger, but you are probably using the same or more gas. I just have a very hard time believing that a TT sports car is rivaling hybrid gas mileage on the freeway. __________________ Car Sold! Pleasure being a part of the Z community. New ride: 2015 GT-R - 647 WHP / 641 WTQ (e85) & 543 WHP / 519 WTQ (91)

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