Pulley upgrade, which one?

[Scuba Steve]

My 2000 Miata is currently in winter storage and I am starting to purchase upgrades for this spring. My current plan is to upgrade the pulleys, replace the elf with a PC PRO, add a wideband, and possibly purchase a BTB and bigger radiator.

I plan to buy anodized pulleys this week, do you think I can replace the 115/65pulleys with 120/65 pulleys? I am running stock injectors with a Walbro 255. I don't have an extra injector and have not had any ping with MN 92 octane.

[chuckerants]

Steve, I would think that would depend on what your AFR is now. With the 120mm + the PC Pro + the WBO2 at the same time, you should be able to adjust the AFR really easily.

On my car, with the 5th injector, I have never been short of fuel eveb though I have the OEM fuel pump. With the new fuel rail, I have to turn the PC Pro down all the way. I also need to turn down the 5th injector down a little too.

So I guess, yeah, the 120mm should be ok as long as you can monitor the AFR.

[Mathrips]

I am running a set of 01 injectors in my 99. It seems to idle and run fine. These are reported to give a little more fuel.

[Tom @ Fast Forward]

The 01 injectors add a lot more fuel. ~12%. Goes from 240cc to 270cc. Nice idea. I think you can go all the way to 310 before idle becomes an issue. At least I have read that on mnet so it must be fact. :)

[cmetzner]

I believe that Gary at TDR recommends installing the larger 270 injectors with every 99-00 kit that he sells.

[Tom @ Fast Forward]

However, E-Cool is a cool way to make up the fuel difference too. ;)

[Mathrips]

E-Cool is the way to add fuel.
The person who got his 99 to run on 310 injectors with stock ECU was also running stock fuel pump. No testing with more fuel pump that I was able to find.

[Scuba Steve]

E-Cool is the way to add fuel.
The person who got his 99 to run on 310 injectors with stock ECU was also running stock fuel pump. No testing with more fuel pump that I was able to find.

So what is this post trying to say.I have 4 auxilary injectors on my FMII from the kit 5 years ago. We do not need to use that technology today.

My preference is to run 4 injectors, and no more. Why is it e-cool to run more?

[Tom @ Fast Forward]

E-cool kills two birds with one stone. Adds a little extra fuel and cools the incoming charge air to take a little heat off before is gets to the cylinder.

[FormerDatsun510Man]

Chuck, are you saying that with the FFS fuel rail it increased the amount of flow of the stock injectors? If so, this has got my interest. Since I am running with an air/air IC I wouldn't mine not needing the 5th injector. I have the JR pill which raises fuel pressure statically to about 75psi, though right now I went back to stock fuel pressure since I found I needed the 5th injector anyway. But if I can figure out a way to run it without the 5th that would be great... simple is good and I would love to be able to tune the entire a/f on my car with just 1 PC Pro.

Steve, I am running nearly the same setup as you with the 120 pulley. I found when the weather was warmer (about 75 deg F) a few days ago that my setup barely could keep the fuel rich enough at 7000rpm with just the stock injectors and no 5th injector running. It would hit about 12.5:1 at engine redline. However, when the weather is cooler now it will hit about 13.5:1 if I don't run the 5th injector. I can get it to run richer at the rest of the rpm range, but it gets lean after 6500rpm.

I think the reason I could even get away with this much indicates that the air/air IC is not flowing terribly well... probably running about 200rwhp with the 120 pulley. Whereas with the TDR the 120 pulley would probably make around 210-215rwhp.

Bill

[Tom @ Fast Forward]

Bill,

It is more like the fuel rail stops the pressure loss. The static pressure on the 99+ is about 62PSI. What I found a couple years ago was that the pressure would drop to about 55PSI under WOT at above 6000 RPM. The big fuel rail lets the pressure maintain the 62 PSI all the way. You can do the math and see the loss. This is really a non-issue at 200WHP and under. It is also a non-issue with 01-05 cars as they have 12% larger injectors.

The gains are probably not enough to eliminate the 5th injector in your case if you still have stock injectors as I think they run out of snuff at ~200WHP even if the pressure is maintained at 62PSI. You really want to stay under 90% DC on the injectors. The 5th that we use is a 48# (~480cc). That is the equivalent of two stock 94-00 injectors and is a real blessing as it does not effect the pressure in the fuel rail at the main injectors. It was never a matter of the fuel pump running out of pressure but rather the pressure loss across the rail with the almost double fuel flow.

I have an electronic fuel pressure gauge and sender if you want to test your pressure. Once I went coldside with the 5th injector, I no longer had a fuel rail pressure so I removed it. Let me know.

[FormerDatsun510Man]

I see what you are saying. I think I will just stick with the extra injector :). Currently I am running a 370cc extra injector.

Tom, what psi do you start running the extra injector when using the PC Pro? The Split Sec map I currently use that worked well on the old PC and ELF starts it at 5psi. Should I move it back down to 0-1psi? Also, what max duty does the PC Pro allow on the main injectors?

I can figure this out myself with some testing, but I thought I would ask the pros first :).

Bill

[Tom @ Fast Forward]

Bill,

What size are your main injectors? Stock?

[FormerDatsun510Man]

Yes, I am running stock '00 injectors with the Walbro 255HP fuel pump. I pulled the JR fuel pressure pill out of the regulator so it is running back at the stock 62psi rail pressure.

Bill

[Tom @ Fast Forward]

Then I would definitely keep the 5th injector.

[FormerDatsun510Man]

Yeah, I was thinking about putting some '01+ injectors in there, but I didn't think of the consequence that this puts even more load on the stock fuel rail. I am going to do as you suggest and stay with the current stock injectors in there and just turn up the extra injector fueling. Besides, that way I could safely fuel the 130 pulley :).

Bill

[Tom @ Fast Forward]

I sell fuel rails too. ;)

[FormerDatsun510Man]

LOL I guess I will eventually need a fuel rail too.