MAF curves with larger injectors - Page 2

Wicked · 05-12-2005, 05:10 PM

Quote:

Originally Posted by QWKSNKE

Any difference if I use a 55# MAF

Not really, its all in the scalars.

Right Nathan, he should not mess with the MAF curve itself.

QWKSNKE · 05-12-2005, 07:09 PM

Quote:

Originally Posted by Wicked

Not really, its all in the scalars.

Right Nathan, he should not mess with the MAF curve itself.

Why? I have been constantly modifying the curve and it isn't dialed in yet.

Wicked · 05-12-2005, 08:09 PM

Quote:

Originally Posted by QWKSNKE

Why? I have been constantly modifying the curve and it isn't dialed in yet.

You're already using the 55# MAF?

Sorry, I was wrong about the 55# maf, if you switch MAF's, you will have to use the new MAF's transform function or develop it yourself.

My comment to Nathan was in response to his question about just changing injectors.

QWKSNKE · 05-12-2005, 08:23 PM

Quote:

Originally Posted by Wicked

You're already using the 55# MAF?

No I am currently using a 42# MAF with 42 injectors. But with aftermarket Mafs you still have to change the MAF transfer in order for the car to be right (refer custom tunes)

Anyways, since the engine rebuild, the tune is not complete (MAF curve, IAC duty, etc.).

The reason I asked these questions is because Wall has 60# injectors and a 55# MAF that he is willing to let go. Since my duty cycle with the 42's is around 90% at WOT, I was thinking of changing over to 60's

86GT · 05-13-2005, 11:35 AM

Any MAF and any injector combo can be used with a tuner. The only reason they sell matched sets is for those that do not have a tuner. The Matched sets that are above the stock vaules are fooling the EEC.

Most of the tuners will enter in the MAF curve supplied by the manufacture and then simply enter in the injector slopes. That is the theory behind it, but the fact is that every car is different and the injectors have different tollerances. This is the main reason people have problems even if they have the flow data from the manufactures.

Cold air kit, conical filters and inlet tubing size and material make up all have a toll on the flow numbers. Most of the MAF manufactures use a test bench for the calibration of a MAF meter. This procedure does not include your intake track therefore there will be some differences. Injectors spray different under different pressures and intake port size. As you can see, it not as simple as it appears, but it can be done.

With all that said the 55# MAF and 60# injectors will work, but it will take time to dial it in. If you have the flow sheet, you should be able to get close. The MAF may not help if you are not pegging the one you have. You can raise the injector size and raise the fuel pressure to lower your injector duty cycle. This will only buy you time tho. The larger injectors will lower the injector duty cycle while maintaining the current fuel pressure.

As a side note, I was told the EEC has a build in limit of 90% duty cycle on the injectors. The Tweecer log will log above 90% but the EEC will limit the injector output to 90%. If this is true then you will run lean up top. It is time to change the fuel pressure or injector size. I have not had the luxury of hitting 90%, so I can not test this.

If you try richening the upper part of the MAF while at 90% Inj. DC and the mixture does not change then it is true.

QWKSNKE · 05-13-2005, 12:06 PM

my fuel press at WOT ususally hits 55 - 60 psi

Italian LX · 05-13-2005, 03:16 PM

Quote:

Originally Posted by 86GT

I have not had the luxury of hitting 90%, so I can not test this.

I have hit 100% before.

Wicked · 05-13-2005, 06:50 PM

I'd try the 60's with the MAF you have now. The new injectors would be easier/quicker to tune in than the new MAF. Might be easier to tune if you do it in two steps.

QWKSNKE · 08-04-2005, 04:13 PM

Quote:

Originally Posted by Wicked

I'd try the 60's with the MAF you have now. The new injectors would be easier/quicker to tune in than the new MAF. Might be easier to tune if you do it in two steps.

Actually it would take way longer. It would be easier to tune a new MAF and injectors because you would have the flow sheet to go by and adjust.

Changing the injectors on a smaller MAF would equal a lonnnng time datalogging

Wicked · 08-04-2005, 04:47 PM

Quote:

Originally Posted by QWKSNKE

Actually it would take way longer. It would be easier to tune a new MAF and injectors because you would have the flow sheet to go by and adjust.

Changing the injectors on a smaller MAF would equal a lonnnng time datalogging

Well, if you can get the flow sheet for the new MAF, why couldn't you get the flow sheet for the old one. Shouldn't you already have it since you have previous tuned the car?

That doesn't really make sense.

05-13-2005, 11:35 AM	#15
86GT Member Join Date: Mar 2005 Location: Sacramento California Posts: 449	Re: MAF curves with larger injectors Any MAF and any injector combo can be used with a tuner. The only reason they sell matched sets is for those that do not have a tuner. The Matched sets that are above the stock vaules are fooling the EEC. Most of the tuners will enter in the MAF curve supplied by the manufacture and then simply enter in the injector slopes. That is the theory behind it, but the fact is that every car is different and the injectors have different tollerances. This is the main reason people have problems even if they have the flow data from the manufactures. Cold air kit, conical filters and inlet tubing size and material make up all have a toll on the flow numbers. Most of the MAF manufactures use a test bench for the calibration of a MAF meter. This procedure does not include your intake track therefore there will be some differences. Injectors spray different under different pressures and intake port size. As you can see, it not as simple as it appears, but it can be done. With all that said the 55# MAF and 60# injectors will work, but it will take time to dial it in. If you have the flow sheet, you should be able to get close. The MAF may not help if you are not pegging the one you have. You can raise the injector size and raise the fuel pressure to lower your injector duty cycle. This will only buy you time tho. The larger injectors will lower the injector duty cycle while maintaining the current fuel pressure. As a side note, I was told the EEC has a build in limit of 90% duty cycle on the injectors. The Tweecer log will log above 90% but the EEC will limit the injector output to 90%. If this is true then you will run lean up top. It is time to change the fuel pressure or injector size. I have not had the luxury of hitting 90%, so I can not test this. If you try richening the upper part of the MAF while at 90% Inj. DC and the mixture does not change then it is true. __________________ EEC Analyzer A9M, TwEECer, 306ci, 73mm C&L w Tuner Tube, Cobra Intake, 42# inj, Edelbrock 6037, E303 cam, 155 fuel pump, FPR, 70mm TB, E-Fan, 3.55 gears, Powerdyne 9psi actual 5psi...way more.

05-13-2005, 12:06 PM	#16
QWKSNKE 3v's are slow Join Date: Dec 2004 Location: Here and There Posts: 17,152	Re: MAF curves with larger injectors my fuel press at WOT ususally hits 55 - 60 psi __________________ 2009 Porsche Carrera S 2008 ///AMG C63.. Eurocharge Tune. RIP 2019 AMG GLC43..wife's 03 F250 SD.. Edge Evo, AFE Stage 1 CAI 08 GT. JBA axle back, FRPP springs, FRPP swaybars.. daughter's 01 Cobra vert... wife's I need a new toy

05-13-2005, 06:50 PM	#18
Wicked Friends Join Date: Dec 2004 Location: Pell City, AL Posts: 1,371	Re: MAF curves with larger injectors I'd try the 60's with the MAF you have now. The new injectors would be easier/quicker to tune in than the new MAF. Might be easier to tune if you do it in two steps. __________________ 2001 Cobra 'Vert Procharged and Intercooled 455rwhp/441rwtq Work Car: 2005 Honda Odyssey 400 whp Turbo V6, 6-speed, full cage, H&R Suspension, Brembo Brakes