3500 Rpm

[R33S2]

The reason my car uses heaps of fuel is because of lowish gearing, at 100km/h it sits at 3000rpm and is boosting at that level, its good to have that sort of power on tap but I dont need it really for normal driving.

I've been pondering this dilema for some time now.

I could get a bigger turbo that has more lag and people with these say if they drive sensible they can get good milage, but no bottom end and large outlay.

Now if I could stop boost (run NA using standard BOV) to 3500 I could have the best of both. To do this I would need a soleniod that cuts in/out at 3500 (or 3200 etc) for when I'm doing a long trip.

The BOV would also have to work normally and is pos if I have another solenoid that activates the first.

I'm using the MAF based Microtech so I hope its possible.

[paulr33]

boost doesnt use fuel or affect your economy. the economy is driven by rpm and airflow meter load. airflow meter reads more air, the fuel cells drop a little on the map and it will use more. there is more to your problem than you are thinking of. upgrading the turbo is a pointless exercise. boost does not affect your fuel economy, airflow and revs do.

so whats your fuel economy like? mine sits at 3000 at 100km/h and i can get 600k's to a full tank on the highway or around 400k's city driving with some mild high powered runs.

[paulr33]

ah crap i just read your using a microtech. well is it tuned properly? what the afr's like on cruise/low load? or is it just max power tune?

does it support 02 feedback? if not then dont bother replacing the 02 sensor as its not used.

your likely reasons for bad economy (based on microtech)

- light load / cruise map area is not tuned and runs default map values ie: most likely mega rich

- microtech doesnt support closed loop / 02 feedback

- if ecu suppports 02 feedback / closed loop then 02 sensor is dead

get back to me regarding those

[paulr33]

if you do find out microtech doesnt support closed loop / 02 feedback you can still get good economy it just takes a lot longer to tune and fixen up. my powerfc is tuned with 02 feedback off and im getting the economy i posted above. so if thats the case, you need to have your car tuned on the road with a wideband sensor. basically drive around some local suburbs at normal speeds (and normal load) and tune around that. theres no need to do any max power, full throttle runs.

ie:

cruise at 30km/h in 3rd gear

cruise at 40km/h in 4th gear

cruise at 20km/h in 2nd gear

cruise at 60km/h in 5th gear

do those sort of road tuning 'areas' on the map and that should sort out most of the light load / low cruise areas.

[R33S2]

Thats interesting I thought that as the MAF saw more pressure it increased fuel etc to accomdate, the boost gauge on the microtesh dash unit shows boost at 3000 and assumed it would be compensating.

I recently had a problem with ignition and havent checked usage, but I was getting 10km/l and it was down to 8 before I fixed it. I specified an economic tune as it was daily driver.

Thanks for your replies Paul but the question was Is it possible? but youv'e cleared the practicle side.

QUOTE(R33S2 @ 10 Jan 2006, 08:04 PM)

Hey Dan

I was talking to you about turbos and fuel consumption last thursday and how my car sits on boost at 100+ km/hr and never got to ask if there is a compatiable turbo that wouldn't see boost till 3500rpm or so, I haven't got a clue if this is a good idea or not but am interested to hear your opinion.

Well , funny thing is my highway mileage is friggin awesome. I get around 750k's to a tank on the highway....but only 350-400 around town. I can drive along in 4th gear at 100 and still not be on boost lol.

[paulr33]

the ecu (stock or microtech) has no elec map sensor (pressure sensor) so all it does is measure air coming into the engine. whilst if it measures more air coming it will use more fuel, it wont measure pressure (ie: boost) so you can have 12psi or 2psi in the manifold and it wont matter, all the ecu cares about is how much air is coming in.

an ecu such as powerfc djetro which is a map sensor ecu uses a map sensor instead of an airflow meter and guesses how much air is coming in based on pressure

it just sounds like your right foot is the main culprit. get a friend to plod around in your car for a few days, you may be surprised about the economy you get if someone else drives it