I'm just curious to see what kind of fuel economy this setup would yield. I'm building up my motor soon (currently a turbo D-series) w/ bottom-end hardware as well as a standalone that can handle 550cc/min injectors. Since I still intend for my car to be a daily driver, what sort of fuel mileage can I expect? Figure commute-style driving (little to no boost), not *****-to-the-wall-let's-outrun-the-cops style... I hope to get at least 20mpg!!!

 

in a d-series, your concerned about gas milage?? is that a joke? ha ha ha
try a h22 boosting 14!!! and i'm happy with 91 and octane booster

 

well i still get DIESEL gas mileage with 370's and a V-AFC on my built turbo d16... easily over 30 mpg on every tank. it's all about tuning. and daily driving, i boost 5.5 psi.

 

The beauty of a standalone is that it relieves you from Piggyback Hell and will allow you to tune your car to its true potential. Properly tuned, your car should get just as good, if not better, mileage than stock. I still get ~30mpg with my Hondata and 440's.

Sonny

 

i got 550s and a zdyne,i get 25-29mpg around town,30-35mpg highway.

 

If you're going to spend $3K+ on turboing your $2K built motor the last thing you should worry about is gas mileage.

 

ive got a bosch inline pump and stock injectors.. im boosting about 4psi and my gas mileage is ****.. about 20mpg..

 

Running WAY rich, beating and flogging my car, I've been getting right at 20-22 MPG.

Z-Dyne and 550's here as well.

 

I think the point is as long as you're tuned properly and the ECU is running closed-loop off the O2 sensor there is no reason in hell you should be getting poor gas mileage no matter how big your injectors are or how much boost you're running.

Drop your CR, and the engine has to work a little harder off boost to make up for that, so your mileage will suffer somewhat.

 

755cc with a hondata

22-25 in the city
28-32 on the highway

 

it doesnt matter how big of a fuel injector you get as long as the ecu can control them correctly.

ie say you had a hondata with 340cc and then dropped in 750cc there should be no difference in fuel economy as the hondata can correct for the larger injector.

liam

 

Wow... ok great... I'm not as worried anymore. Thanks for the input!

So if that's the case, couldn't I just get massive injectors and not have to worry about future increase in power? Incidentally, is the normal practice to run stock (40-46psi) fuel pressures at the fuel rail?

 

With larger injectors you decrease the duty cycle (the amount of time the injector is open) to decrease the fuel. Unfortunetely there's a limit to how quickly the injector can be opened and then closed again. Huge injectors, say 1600cc, flow too much even at the lowest setting to maintain a good idle. Another reason to get them is that they're expensive. Unless you find a deal on injectors they can start to get really expensive around the 700cc mark.

 

Hey guys, just a quick question. What duty cycle are you guys using on 550's in your cars? I've got mine with a stock fuel pressure regulator, and 550's. 1.08 duty cycle is the figure in my z-dyne and I'm getting alot of "thrumpety" idle problems and soot on the ground behind the tailpipe. Also, LONG starting problems on the car. I like to spin and spin, almost like it's flooded and cleaning itself out... Z-Dyne's showing 60% enrichment for startup.

Any ideas? I've taken it down to 1.00 in a range of areas on my unit, but didn't notice any changes... Plugs are 2 ranges colder than stock.

Help please Starting issues, I'm THINKING might be attributed to leaky injectors


[Modified by SiR Kid, 10:18 AM 11/29/2001]

 

1st off,you gonna have problems with spark plugs that cold,i couldnt even run 1 colder without throwing a black cloud + putt putt idle out on a cold start,i put stock plugs back in,i run exact same pulse at 1.08 with a 25% fuel enrichment,been starting good at any temp from zero degrees to 100 outside.

 

DAMN SWEET! Exactly what I needed to know. Any problems with burning electrodes with stock plugs?

 

so far no,plugs look good,but highest boost ive reached so far is 14psi running sunoco 94 + octane boost.

 

I too have had an issue with stumbling idle and rough starts, perhaps it's my plugs?? Never thought of that. Right now I use RC440cc injectors and the V-AFC and I still get over 300 miles to the tank if i'm nice, 270ish if I flog it alot. BTW, anybody else with a D16 w/ large injectors and a V-AFC, how much do you trim the car at idle and WOT? Right now I'm at -35% idle and -18% WOT @.60bar, just curious to compare settings.

 

I've come to the conclusion that the -xx% settings at idle are only useful for about the first minute the car is running. Before the O2 sensor heats up, the car takes a wild-*** guess on how much fuel it needs based on the MAP and IAT... you have to adjust on the VAFC for it to start so it trims the MAP reading and the ECU subtracts fuel. Once the O2 sensor gets up to operating temperature the ECU goes closed-loop and it automatically compensates for whatever injectors are in there (up to a point of course) and I think the MAP input is completely ignored since it is no longer fuelling from a "map" but from a feedback loop instead.

 

Interesting, but I think the MAP must be used to a degree, because by either drastically increasing or decreasing the percentage at idle, I can make the car stumble and nearly stall since the ECU is trying deperatley to correct fuel measures, meaning the ECU is reading the MAP at idle. Give it a try, you'll see what I mean.

 

Okay... consider this scenario then... I'm planning on around 275 crank hp from my D-series (after a build-up of course). Using 550s at a stock static fuel pressure of ~46psi... 550s should be good to around 270-280hp max. In the event I want to run more boost, say 320hp for example, what do I need do? RC's injectors for anything above 550cc are wayy expensive. Can I just stick in an adjustable fuel pressure increaser like the B&M unit and solve the issue that way?

 

It depends on two things:

1) Your current maximum injector duty cycle
2) Your current maximum fuel pressure

With you current setup, if you're only pushing the injectors to 70% max duty cycle and your fuel pressure is 50 psi max, then you have a lot of room to play as long as you've got a decent pump. You could increase your max duty cycle to 80% (I wouldn't exceed 80%) and up the fuel pressure by 10psi and deliver a lot more fuel. I wouldn't exceed 60psi of fuel pressure...it kind of defeats one of the nice things about having a standalone.

Sonny

 

[QUOTE]550s should be good to around 270-280hp max. In the event I want to run more boost, say 320hp for example, what do I need do?[ /QUOTE]

550s can support up to 500hp

 

It really depends on how well the car is tuned. I am running 1100cc MSD Injectors in my Prelude with Hondata stage 4B. I have a perfect idle, and these injectors can be had for relativley cheap. Mine were 365 for the set from JG. I got the base MAP from JG as well, and just fine tuned it. My around town mileage is about 22-24mpg, and on the highway I get about 28-31mpg. of course when I really hammer the car, the mileage drops considerably. I use the big injectors to handle the high boost at the track. I am tuned to run 93 on the street. Seriously though as long as you have the car tuned your mileage shouldn't suffer at all driving normally.

 

Ok, define driving "normally". LOL! Normally for me is shifting at 6-7K and downshifting to 3rd to go 60mph around 35mph curves.