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I pulled the heads off my B5 S4, ported and polished them. It's amazing the imperfection in these motors, especially under vacuum conditions. Like cruising down the road at highway speeds expecting to get good gas mileage!
After taking my resonator off the exhaust for better flow and adding new K04's, and doing all that port and polish work on the heads and intake manifold. I have personally recorded 40.2mpg on a 50 mile trip, doing 65mph on flat ground.
I'm stage 2+ (turbo back exhaust, no cat or pre cat) with Tiptronic. I get around 16-18 mpg and that's pretty much all city stop/go driving. Running 93 octane.
I get around 21-23 when doing some highway driving.
There are actual mpg, not dash read outs. I record my miles per tank, then divide by gallons when I fill up.
For kicks, I kind of want to get or figure out how to tune my stock ECU so I can see what the mpg difference is among tunes. I mainly need to code out my EGT and rear o2's.
I've been kicking around the idea of getting the programmer that will allow me to change tunes on the fly. Similar to Cobb's Accessport. Then I can run stock during the commute to work, and stage 2+ on the weekends. I mainly want the programmer so I can store all of my tunes, and not have to physically swap ECUs to change all the time...
I get about 20 mpg mixed. I think for what it is thats fantastic. Chipped twin turbo AWD car. The normal 2.8 cars arnt even much better. I would not consider 21mpg crap. Thats fantastic, my 1.8T A4 got 25 at best mixed. The guy claimed 40mpg is either not doing the math right or exaggerating, it will never happen on a 6 cylinder Audi.
My 90 Turbo Grand Prix I have, when I drove it, I could never get any better than about 14mpg lol.
Last edited by Prospeeder; 01-07-2016 at 04:32 PM.
The b5 s4 like most Audi's have variable valve timing which is designed to achieve the best of both worlds, good gas mileage while still being able to advance the timing under boost. The main reason these cars get around 25mpg is because of the imperfection in the intake and exhaust ports under vacuum conditions when port velocity is most important, so by making my engine more flow coefficient under vacuum conditions I'm able to achieve excellent gas mileage. Oh and yes I have done the gas mileage math after filling up, and my b5 s4 dash mpg average is spot on.
Before and after picture of the port and polish work on my S4 heads.
So, you have my attention. Did you do this work yourself? What's your background, and how did you know what to do here?
Yes, I did do this work myself.
I don't have a school background in engines or anything. I simply have been blessed with being around the right people/mentors. All I'm doing is increasing port velocity by decreasing drag. The imperfection in the ports and combustion chamber of any engine are the major problem for carbon build up which causes hot spots and silent detonation. By polishing up the head and piston like a mirror the carbon can't cling to the surface and build up, because we all know carbon build up is the main killer of any engine. The mirror finish helps in reflecting the energy, so that all the thermo kenetic energy goes into pushing down on the piston instead of absorbing into the parts. Heat/combustion = energy! the more heat that is absorbed by the head and cylinder the more potental energy that is lost. This is a problem with all internal combustion engines. If you have any questions feel free to ask!
46-47mpg recorded the other day on flat ground along the river road, doing 60mph with the cruise control set. - 5400ft / 78 Degrees -
Upgrades are stock Ecu, (port and polishing the heads and intake manifold = 60-70% of the overall increase) then some K04's, tuned length headers, wrapping the stock exhaust back to the muffler after removing the resonator (for better flow and heat energy the more you can increase the exhaust temp the faster the pulse waves flow out the exhaust) and I'm running the stock air box.
46-47mpg recorded the other day on flat ground along the river road, doing 60mph with the cruise control set. - 5400ft / 78 Degrees -
Upgrades are stock Ecu, (port and polishing the heads and intake manifold = 60-70% of the overall increase) then some K04's, tuned length headers, wrapping the stock exhaust back to the muffler after removing the resonator (for better flow and heat energy the more you can increase the exhaust temp the faster the pulse waves flow out the exhaust) and I'm running the stock air box.
Interesting! You must have a nice set of gears in that B5! We all know it is the stopping & starting with red-light idling that kills MPG in the city. Tame highway driving and keeping something like cruise control can help to get the numbers up but you should be able to do better without cruise! But upper 40's? What other tricks are you using? Overinflated tires, windows up/AC off? I'd think you were drafting too - between 2 large semis, to get numbers like that!
If porting, polishing, & ECU changes gets these results, wouldn't it be more widely done?
11-22-2015, 10:43 AM
