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Old 11-26-2006, 03:33 PM   #1
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Default a/f ratio

hello,

can anyone help,just had my car rolling roaded it gave 186 bhp f/wheel or 158 bhp at the r/w.running at 9 psi at 4,000 rpm a/f was (14.1) and at 4,500 rpm.
The miata(MX5) 1.6 ltr intercooled with 1.8 injectors begi afpr, greddy td04 15g,bipes acu, forge wastegate forge boost controller running 14 deg timming with 4 deg taken out at 3000 to 4000 rpm + 1 deg to temp.(1.8 flywheel and techi 1.8 organic uprated clutch.

the base fuel pressure is 45 psi and the begi afpr with the vac line disconnected reads 70 psi. something not right..any comments or advice is welcome..
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Old 11-26-2006, 03:53 PM   #2
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Your no load pressures are too high. I'm guessing that you're still running your oem pump and you're trying to work the hell out of it to get more fuel. More pressure does not mean more flow. In this case, as you increase pressure, you have less flow. You'd probably have ok afr if you ran 6 psi and lowered your pressures to increase flow. And you'd probably still have 160 hp at the wheels. But you won't blow up your motor.

You need a new higher duty fuel pump for 9 psi. Replace the filter at the same time.

I hit 165 + rwhp with basically the same setup at 6 psi.
https://www.miataturbo.net/forums/showthread.php?t=5716
https://www.miataturbo.net/forums/vb...o=view&id=1251

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Originally Posted by greenmachine View Post
hello,

can anyone help,just had my car rolling roaded it gave 186 bhp f/wheel or 158 bhp at the r/w.running at 9 psi at 4,000 rpm a/f was (14.1) and at 4,500 rpm.
The miata(MX5) 1.6 ltr intercooled with 1.8 injectors begi afpr, greddy td04 15g,bipes acu, forge wastegate forge boost controller running 14 deg timming with 4 deg taken out at 3000 to 4000 rpm + 1 deg to temp.(1.8 flywheel and techi 1.8 organic uprated clutch.

the base fuel pressure is 45 psi and the begi afpr with the vac line disconnected reads 70 psi. something not right..any comments or advice is welcome..
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Old 11-26-2006, 04:13 PM   #3
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thanks ben,for your advice,
i have fitted walbro 255 fuel pump and have new fuel filter.i did clamp the fuel return line and it read 130 psi.i think i will drop the boost from 9 to 8 psi.
any comments
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Old 11-26-2006, 04:18 PM   #4
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which walbro 255--standard or high pressure? I'm guessing hp from your max pressure test. Was it installed before or after the dyno run?

I'm running less base and pulling more timing than you, and I need to bring down the base a little more because I'm on the edge. I always run US spec 93 octane.
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Old 11-26-2006, 05:15 PM   #5
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9psi is just a little too much for the 1.8l injectors.

i see your inital base pressure goes to 70psi, probably why you see a rich spot on intial boost. you might want to back it off to 50psi (especailly with the 255). Then tune your max pressure to 100psi. so if you're hitting 8psi tune to a max off 100psi when you hit 8psi.

You're 14.1 spike could also be ping, you're not pulling very much timing, acutally none at all if you weren't advanced. At least pull to 8* and try tune the fuel a bit better and try again. But I think you'll see you've reached the limits of the injectors.
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Old 11-26-2006, 05:29 PM   #6
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Quote:
Originally Posted by braineack View Post
9psi is just a little too much for the 1.8l injectors <snip>
I disagree. 9psi is potential to 215 crank hp with the 1.8s and factory ecu. At the limit, but not over it. At 186 crank, he's out of fuel but it's not injectors. My 9 psi plots are posted.

Definately too much timing based on my experience.
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Old 11-26-2006, 05:34 PM   #7
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next time post in the correct forum or I'll just delete it
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Old 11-26-2006, 06:10 PM   #8
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Quote:
Originally Posted by Ben View Post
I disagree. 9psi is potential to 215 crank hp with the 1.8s and factory ecu. At the limit, but not over it. At 186 crank, he's out of fuel but it's not injectors. My 9 psi plots are posted.

Definately too much timing based on my experience.

yeah ive seen your plots and ive seen my own. i wouldn't try any more than 9psi. with teh begi fmu im sure i would see better results. but with a better exhaust you might see worse.

I determine 215hp at the crank to be 180 at the wheels, which should be somewhere between 6-8psi.
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Old 11-26-2006, 06:14 PM   #9
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Quote:
Originally Posted by Ben View Post
I disagree. 9psi is potential to 215 crank hp with the 1.8s and factory ecu. At the limit, but not over it. At 186 crank, he's out of fuel but it's not injectors. My 9 psi plots are posted.

Definately too much timing based on my experience.
hello ben,

the feul pump and filter was fitted just before rolling road,as for timing the bipes acu is at the lowest setting(no pinking)i read on that the 1.8ltr injector(230 cc) should be good for 10 to 11 psi off boost also that the 1.6 ecu will take no larger than (270 cc) injectors but this might be wrong.
i wonder what is the largest injectors on the 1.6 ecu.
just a thought the begi afpr has the bleed adjuster screwed right in.i was told to leave like that.

any comments thanks....
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Old 11-26-2006, 06:27 PM   #10
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Quote:
Originally Posted by braineack View Post
yeah ive seen your plots and ive seen my own. i wouldn't try any more than 9psi. with teh begi fmu im sure i would see better results. but with a better exhaust you might see worse.
I didn't dyno with the vortech for comparison to the begi. After new exhaust the 1.8's wouldn't cut it at 9 psi on my car, but I would make the same 185 rwhp at lower boost, and the injectors would be fine.

Quote:
I determine 215hp at the crank to be 180 at the wheels, which should be somewhere between 6-8psi.
Not with factory exauhust. Neither my car or the op have opened the exhaust up.

I think what's important here is that the injectors are limited to around 215 crank and 180 rwhp. This remains true if it takes 1, 6, or 10 psi to get there. He's running lean at 160 rwhp, so unless the injectors are jacked, there is another issue.
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Old 11-26-2006, 06:38 PM   #11
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thanks braineack,
i am in the u.k and use 99 octane fuel,can't hear any knocking but do you think ishould add more retard to timing.setup is 4 deg of retard to start at 3,000 rpm to 4,000 rpm and every 50f 1 deg retard to temp.
i read on that the 1.8ltr injector(230 cc) should be good for 10 to 11 psi off boost also that the 1.6 ecu will take no larger than (270 cc) injectors but this might be wrong.
i wonder what is the largest injectors on the 1.6 ecu.
just a thought the begi afpr has the bleed adjuster screwed right in.i was told to leave like that.

any comments thanks....
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Old 11-26-2006, 07:32 PM   #12
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Quote:
Originally Posted by greenmachine View Post
hello,

can anyone help,just had my car rolling roaded it gave 186 bhp f/wheel or 158 bhp at the r/w.running at 9 psi at 4,000 rpm a/f was (14.1) and at 4,500 rpm.
The miata(MX5) 1.6 ltr intercooled with 1.8 injectors begi afpr, greddy td04 15g,bipes acu, forge wastegate forge boost controller running 14 deg timming with 4 deg taken out at 3000 to 4000 rpm + 1 deg to temp.(1.8 flywheel and techi 1.8 organic uprated clutch.

the base fuel pressure is 45 psi and the begi afpr with the vac line disconnected reads 70 psi. something not right..any comments or advice is welcome..
Get yourself to a real dyno facility. That dyno you were on doesn't even do printouts?!? I think you want something a little more modern. First HP peak should not be at 5500 RPM, even with a smallish TD04.

I would make sure that you get more fuel into the motor as it's quite obvious that the A/F only gets right once the turbo starts to run out of steam (although I would suspect that's the car choking on it's exhaust.)

Mark
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Old 11-26-2006, 09:27 PM   #13
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Quote:
Originally Posted by greenmachine View Post
thanks braineack,
i am in the u.k and use 99 octane fuel,can't hear any knocking but do you think ishould add more retard to timing.setup is 4 deg of retard to start at 3,000 rpm to 4,000 rpm and every 50f 1 deg retard to temp.
If you dont hear knock then you are ok. If you have a 94 or earlier, then you can watch the oil pressure gauge to make sure. it will start to spazz out if it knocks.

Quote:
i read on that the 1.8ltr injector(230 cc) should be good for 10 to 11 psi off boost also that the 1.6 ecu will take no larger than (270 cc) injectors but this might be wrong.
i wonder what is the largest injectors on the 1.6 ecu.
I'm running 305cc injectors on the stock ecu, without trouble. Andy Floyd is running 330cc injectors.

Quote:
just a thought the begi afpr has the bleed adjuster screwed right in.i was told to leave like that.
you should review the installation instructions of the begi fmu. the bleed screw adjusts the amount of rise of fuel pressure. the top screw only adjusts the pressure at 0 ~hg. Both need to be tuned properly. Since the OEM ECU with always trys to dump more fuel at the top end, you could be just shy of the max pressure you want to hit. You should really get a gauge on there and tune the pressure properly and make sure you are hitting 100-110psi of fuel at 9psi.
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Old 11-27-2006, 11:18 AM   #14
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thanks for your help.....
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Old 11-27-2006, 12:19 PM   #15
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Quote:
Originally Posted by braineack View Post
If you dont hear knock then you are ok. If you have a 94 or earlier, then you can watch the oil pressure gauge to make sure. it will start to spazz out if it knocks.



I'm running 305cc injectors on the stock ecu, without trouble. Andy Floyd is running 330cc injectors.



you should review the installation instructions of the begi fmu. the bleed screw adjusts the amount of rise of fuel pressure. the top screw only adjusts the pressure at 0 ~hg. Both need to be tuned properly. Since the OEM ECU with always trys to dump more fuel at the top end, you could be just shy of the max pressure you want to hit. You should really get a gauge on there and tune the pressure properly and make sure you are hitting 100-110psi of fuel at 9psi.
Hello,

thanks for your help.If I use larger injectors on the standard 1.6 ecu like 305cc would I see any more power and does this affect idle and emissions in any way.
also the bleed screw on the begi when screwed in does it give less or more fuel pressure and does this only happen when on boost.

i was told when the bleed screw on the begi is screw in it should give you 6 psi fuel to 1 psi of boost or is this all wrong.

thanks for any help you can give
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Old 11-27-2006, 12:28 PM   #16
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you will need to pretension your afm some more and reset your aic to achieve the proper idle, with 300 cc injectors. what are you runing for Intercooler if your intercooler isnt up to the task you will be blowing alot of hot air and not make as much power as you should i hit 200 dynojet whp at 8 psi on a larger turbo and a stock 1.6 fuel system and 12-1 rising rate regulator that is 50-60 bhp more than you and my af's where in the 12's rising to 12.7 post a new cat so yeah you need to cool your mix down and let the turbo breathe. more fuel if metered correctly will up the power but you just cant dump buckets of fuel at it and hope for the best go find yourself a better dyno and look into a better intercooler. jus tmy 2 cents hope they help
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Old 11-27-2006, 12:35 PM   #17
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You should be able to tune the injectors in such a way that you will idle just as well as stock. Meaning a perfect 14.7 AFR. Then they will be able to support higher HP demands. You can do so by adjusting the idle mixture screw on your AFM or adjusting the spring tension on the unit. I am running 305cc injectors on the stock ecu and AFM. Just took 10secs to tune.

The bleed screw on the BEGi unit can acutally change the rate of rise all the way from 1:1 to 12:1. The slightest turn can increase the pressure 20psi. The tighter the bleed screw the less the venting. Which means more air is pushing down against the piston and clamping off the retun line. This means greater fuel pressure. And adversely, the more loose a setting the more air gets bled off and the less the pistion clamps down on the return line, so less fuel pressures.

the only way to know for sure is the get a pressure gauge and install it on the fuel line. this way you can tune the unit exactly to your needs. $15 at a hydraulics shop can get you everything you need.

You'll tee the gauge in the feed line and tune from there.

First off you want to make sure you adjust the top adjustment screw. So turn on the car and watch the gauge at idle. It should be at 35psi. Remove the vacuum line from the FMU (kink the line so there is no leak) and watch the fuel pressure increase. It should jump up. Turn the screw to tune. you'll want it somewhere inbetween 50-60psi. Closer to 60psi if no o2 clamp is being used on your system.

Now is where the fun part beings. Make sure you get about 4' of fuel hose that the gauge tees off of. You can stick the gauge under your wiper blade and go out for a drive. Get into full boost and watch your fuel pressures. depending on the postion of the bleed valve you may see lots of fuel pressure or little. You want to adjust it to be at 100-110psi at full boost. If you go less boost, go back and adjust it. More boost, again, adjust it to 100-110psi. It's never recommended to run more than that for various reasons.

At 100psi of fuel the 1.8L injectors can handle around 215BHP or 180rwhp.
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Old 11-27-2006, 12:46 PM   #18
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you will need to pretension your afm some more and reset your aic to achieve the proper idle, with 300 cc injectors. what are you runing for Intercooler if your intercooler isnt up to the task you will be blowing alot of hot air and not make as much power as you should i hit 200 dynojet whp at 8 psi on a larger turbo and a stock 1.6 fuel system and 12-1 rising rate regulator that is 50-60 bhp more than you and my af's where in the 12's rising to 12.7 post a new cat so yeah you need to cool your mix down and let the turbo breathe. more fuel if metered correctly will up the power but you just cant dump buckets of fuel at it and hope for the best go find yourself a better dyno and look into a better intercooler. jus tmy 2 cents hope they help
thankyou,the intercooler is from 2ltr ford cosworth(turbo u.k cars) standard they are 210 bhp,but the intercooler on that car can make max 320 to 350 bhp.
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Old 11-27-2006, 12:48 PM   #19
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ok just thought i would ask as everyone else took it forgranted, good luck and happy tunning
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Old 11-27-2006, 12:57 PM   #20
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Originally Posted by braineack View Post
You should be able to tune the injectors in such a way that you will idle just as well as stock. Meaning a perfect 14.7 AFR. Then they will be able to support higher HP demands. You can do so by adjusting the idle mixture screw on your AFM or adjusting the spring tension on the unit. I am running 305cc injectors on the stock ecu and AFM. Just took 10secs to tune.

The bleed screw on the BEGi unit can acutally change the rate of rise all the way from 1:1 to 12:1. The slightest turn can increase the pressure 20psi. The tighter the bleed screw the less the venting. Which means more air is pushing down against the piston and clamping off the retun line. This means greater fuel pressure. And adversely, the more loose a setting the more air gets bled off and the less the pistion clamps down on the return line, so less fuel pressures.

the only way to know for sure is the get a pressure gauge and install it on the fuel line. this way you can tune the unit exactly to your needs. $15 at a hydraulics shop can get you everything you need.

You'll tee the gauge in the feed line and tune from there.

First off you want to make sure you adjust the top adjustment screw. So turn on the car and watch the gauge at idle. It should be at 35psi. Remove the vacuum line from the FMU (kink the line so there is no leak) and watch the fuel pressure increase. It should jump up. Turn the screw to tune. you'll want it somewhere inbetween 50-60psi. Closer to 60psi if no o2 clamp is being used on your system.

Now is where the fun part beings. Make sure you get about 4' of fuel hose that the gauge tees off of. You can stick the gauge under your wiper blade and go out for a drive. Get into full boost and watch your fuel pressures. depending on the postion of the bleed valve you may see lots of fuel pressure or little. You want to adjust it to be at 100-110psi at full boost. If you go less boost, go back and adjust it. More boost, again, adjust it to 100-110psi. It's never recommended to run more than that for various reasons.

At 100psi of fuel the 1.8L injectors can handle around 215BHP or 180rwhp.
thanks again,i shall try this the weekend now.
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