i am putting my rtek 1.7 and 720cc secondaries in pretty soon and i was just curious...since rtek will reduce secondary fire to 3500 rpm will my gas mileage be significantly reduced since i usually cruise at 80mph or 3500 rpms on the highway...?


-Matt

 

3MPG City
4 MGP highway

 

Likely will, but if you have the secondary injector studder (3800 rpm hesitatio) it will be more likey going off and on constantly, I know mine was, not really something you want to happen. My fuel milage with the 1.5 went down a little, but I still manage 550-600km's on the highway (car runs lean) but i have the 550's all the way around.

So yes it will change but you are more likely drive more "spirted"

 

Also curious on this subject

 

It was my understanding that the Rtek chip ran a little rich... Supposedly Rtek 2.0 will be out soon though. And will give you about as much control as most standalones with out the price tag

 

I get about 15-16 mpg with mostly city driving. I kept it under 4krpm for a tank once and got about 20 mpg - that was with a lot of highway driving at about 3500 rpm, ~80mph.

 

Likely will, but if you have the secondary injector studder (3800 rpm hesitatio) it will be more likey going off and on constantly....
what do you mean????

 

I got the 1.7 and 720s. I am getting about 22-23 mile/gal. 80% highway, 20% street.

 

It will make no difference to mileage. When the secondary injectors start to fire the pulsewidth of all four injectors is halved. The amount of fuel injector immediately after the transition is exactly the same as immediately before.

 

I got about 17 mpg composite with 60% highway and 40% city.

On my car the hesitation got worse--I think I know why, the change to 3500 rpm is not good. Basically the secondaries are coming on earlier with insufficient airflow in the secondary runners.

Right now I'm running Megasquirt for fuel and changed the transition to 4000 rpm--it helped alot. Soon I'll be changing the transition to a rpm/map trigger and should be able to totally remove it.

 

yeah the staging wont affect the gas milage really.... my rtek cured my 3800 hesitation amazingly

 

oh man, 20+ mpg would be brilliant! haha

 

I would say this is probably not the case. The secondaries do not fire unless there's sufficient load (at low load the ECU will fire just the primaries even above 3800rpm). To produce enough load to trigger the secondary injectors you need to open the throttle far enough. Unless your at very light throttle, the secondary throttles are open and flowing.

 

Yep--only happens on very light throttle--look at the attached graph.



Look at the AFR reading jump up during transition and notice the throttle (S4) is only 93% and rpm slowly increasing. The primary duty cycle is only at 27% so there is no real need to transition to secondaries. The software is being changed to trigger transition based on map and rpm setpoints. We'll see if that ends up fixing the hesitation--I think it will.

Maybe today I'll try a high transistion rpm and just see what it does under light throttle.

Scott

ps-Oh yea make sure you look over to the left on the scale, otherwise these logs can be a little misleading.

 

On my 1.5 I am doing on average 18MPG with 80-90mph highway driving 80+% of the time.

The best mileage I've ever gotten was on the back from Sevenstock on the downhills. I did 26mpg!!!! But then the uphill section I did 17mpg so it evened it out.

Really the mileage is dependant on your foot/speed/RPM's more than ECU.