First Dyno Run - Surprising Outcome...

First dyno run with a surprising outcome because I was expecting a lean condition with the 24# injectors and instead it's rich. Three back to back runs at temp (190*) were very consistent (421, 422, then a 423rwhp). Lowering the fuel pressure on the third run from 41 to 39 made no change in the air fuel.

What do you make of this dip in the air fuel between 3800 and 5500 rpm? Time for some tuning, 42s, ditch the FMU?

Here's the set up:
306 shortblock
9.7:1 comp
Edelbrock Performer 5.0 heads with 1.94/1.60
Port matched GT-40
65mm TB
75mm Pro-M
Port matched 1 5/8 LT w/ 2.5 X-pipe, dynomax superturbo and turndowns
Vortech V-2 SQ S-Trim @ 10# boost
24# injectors in stock fuel rail
190 in-tank w/ T-Rex auxillary
10:1 FMU
Autolite 3924 @ 0.035"
10* initial timing
MSD 6AL BTM set at 1* retard per pound of boost
93 octane pump gas
39psi fuel pressure setting -- 90psi at 10# boost
Weather: 71*, 84% humidity, 30.02 pressure, 79* at air filter intake

sweet man, congrat on the #'s

Did you read the plugs after? I'll wager that they were showing up a little white with your boost levels and high compression. I'd switch to autolite 3923's.

I pulled a few plugs and yes they are white -- no specs on them (meaning no aluminum or black dots indicating detonation).

Well the dip is text book fmu. It will aways be mad rich in the midrange and come around up top. 42's and a big meter are where it's at. Try the 23 plugs and see what happens. What cam are you running? Those are very good #'s for an FMU car and conservative timing. When you get the big injectors you can experiment with yur timing and there is where you'll find power!

Cam is a B303 set straight up with 1.7 rockers (510 lift). In my case, it has been a terrific cam for roadracing when the car was NA -- broad torque curve and pulls to the factory limiter. And it appears to me to be sufficient for a blower, too, as it is similar to many of the smaller blower cams on the market today. I don't have the typical idle or light throttle bucking complaints. I can cruise at 1700rpm in any gear without the bronco bucking, NA or blown. It's served me well and I just haven't found a reason to replace it just yet.

I'm leaning toward 42s, ditching the FMU, and having a Superchips Custom chip burned and dynoed over at Johnson Motorsports in Mobile, AL. Monte at JMS really impressed me on the phone with the attention to detail he wants to take on my car given I'm roadracing it, by actually simulating a top speed run down a 3/4 mile straight on the dyno, insuring a consistent and safe tune. With the FMU, I don't care for the extended high fuel pressure during open track. Interestingly, one of the Vortech tech guys suggested if I didn't like the high fp, then 42s would work with a 4:1 FMU. That just doesn't make sense to me.

Brent, you mention 42s and a big meter. Please define "big" meter. I currently have a 75mm Pro-M plastic bullet that I can have recalibrated. Are you suggesting a 75mm or the 80mm meter instead?

I didn't see a powerpipe in there either? LOL I'm a pretty firm believer in 4" powerpipes. The 75mm shoud do you just fine. I missed that in your list. You will need it calibrated for 42's but you may want to check with jms if you're going to have a chip done. It may not be totally necessary but i'd check with the experts just to be sure. The 80 will always flow more air but I would think the gains would be marginal for the money unless you could get a good deal on a used one and sold the old one. The guy @ vortech was probably trying to sell you a recal kit. LOL At your power level 42's will serve you very well. As long as the dip in the graph isn't belt slip(and with the A/F dip i doubt it) you'll have alot more response and low end torque.

good luck
make sure you post your results after 42's and the chip. I bet you'll be more than pleased!

BTW you are running the wrong disc in your FMU 24# injectors are suposed to use a #8. That would explain your running rich.

No powerpipe, I'm happy and suprised I have 10# of boost now. Vortech warned me from the start to expect less boost with the S-trim (like 7 - 8#) given the less restrictive heads and exhaust.

JMS recommended 42s and a recal of the 75 Pro-M Bullet.

The belt wasn't slipping, it's plenty tight, and I watched the fp and boost gauges during the dyno run (holding my breath) and as the boost climbed to 10 the fp followed to 90.

By the way, the dyno owner (who builds custom motors for ZR-1 corvettes) suggested a Mass Air Fuel Controller from APEX'i S-AFC http://shop.store.yahoo.com/wotmstore/apsaffuelcon.html to get the air fuel fixed. He showed me one on a customer's Viper and my brother uses one on his 312all wheel hp Lancer EVO VIII with success. It would be an option for me if I was willing to keep the BTM. They tell me the APEX is very common with the import crowd.

Quote:

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Originally Posted by 2stangs69-91

BTW you are running the wrong disc in your FMU 24# injectors are suposed to use a #8. That would explain your running rich.

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I'm running the 10:1 FMU that was supplied by Votech in the S-Trim kit. I've read somewhere that Vortech sells their kits to be fuel "rich". But given the fact that my fuel curve dips rich then comes back up is a concern with a leaner FMU. Wouldn't an 8:1 FMU, in my case, dip less then turn back up and possibly be too lean at high rpm? I think this could create a new problem.

IPPO what pulley are you running?

Running what came with the Vortech (for a 93 Cobra)

6.87" Crank pulley
3.33" Blower pulley
8 rib

I have a set of 42# injectors for sale $200 obo shipped. Lucas injectors only a year old... Went to a set of 50's and a T-trim. also have 24's and matching Pro-m 80 mm. for $275. shipped. thanks Jeff

I made 430 hp with a e-cam, s-trim, 10psi, 10* timming, stock out of box canfields, 100,000 mile stock shortblock(89) and lentech aod, 30# injectors and 3:73 gear. Ran best 11:66 on pep-boy futura radial. no bfg,nitto or et street. I ran socsistant 11:8's I have a 11:90 pass on video. check out my home page. I hope I can see low low 11's on the street tire with the coupe and new combo.

Quote:

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Originally Posted by jtsmg

I have a set of 42# injectors for sale $200 obo shipped. Lucas injectors only a year old...thanks Jeff

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Thanks for the offer Jeff but I have already purchased the injectors and my recalibrated mass air is on the way.

Question for everyone --
I've scheduled a chip dyno tune with JMS Motorsports in Alabama and they suggested before the tune I upgrade my pumps to a 255 non-high pressure in tank and a 255 non-high pressure in line, just to be on the safe side. What do you think about that?

Currently run a 190 intank and T-Rex inline (50/70 - 190).

The so called guy at Vortech is absolutely correct on the fuel pressure w/an FMU..Since he has a 10:1 cal at 10# of boost he should b seeing appx 90+ #'s of fuel pressure.Close to static if u ask me..w/a 4:1 he would only see appx 60#'s of fuel pressure & the same amt of fuel.The cost of a universal recal kit is in the $30-40 dollar range..Hardly an amount to deceive some one for a sale.I agree that a 8:1 would b better in the lower rpm's but would go lean quicker and yes create another prob..the answer imho is 42's.No flames & IMHO...

You are wise to go with 42s, recal your Bullit meter, get the chip burned for your new meter cal, & run the 255 in-tank pump. It's a big nut to crack but worth it IMO.

For those who don't have an injector upgrade in their budget, there is also an old-school method of tuning with your FMU besides the recal: install an air bleed valve on the line going to the FMU. Vortech sells their own whoopy-dee bleeder valve, part 6Z120-010. I doubt you were getting much more fuel in the motor at 90psi than you were down at 65-75 psi, in fact a pintle injector can actually lock wide open over 80 psi if you don't have good electrical grounds and high enough throwback current at the injector, something to watch out for. You can roughly gauge how much fuel you need by calculating what your present injectors were delivering at your torque peak, which is the point maximum fuel demand.