I have an sbc with DFI6, an aggresive hydraulic roller, and comp R lifters. I'm tuning the thing, and it starts right up, runs great at idle and climbs through the rpm range without incident. You can make small rapid increases in throttle at any point in the rpm range and things are fine. However, when you quickly open the throttle a large amount it doesn't rev but makes a popping sound through the intake and a gurgle like when you stab a quadrajet.

I tried adding fuel on the TPS accel enrichment but got nothing so I tried leaning it on tps accel and got nothing again. I've tried 1/16th preload (barely ran) 1/8th (ran as described) and 1/4 (won't start). It could be something valvetrain related, but there doesn't seem to be fire in the intake.

Any suggestions?

 

its lean dude! if it pops out the intake its always lean. richen it up at those cells or if you are in closed loop see if the bar toggles to the right. if it only is doing it with stabs of the throttle, then you need to set the MAP enrich higher,it compensates for the change in airflow and shoots a extra shot of fuel on top of the base fuel map to cover large airflow changes.

 

Thanks for your input. This is the kind of big picture answer I was looking for. I think the map enrichment is low, so I'll try that. It's probably the one thing I didn't tinker with! The EMIC says that it's a fine tuning tool and I ain't ready for any fine tuning so I just skipped it.

I will update this when I get a chance to work on the car. Thanks again!

 

Sure enough it was lean. Now if I can just find that missing 150hp

 

i have a few maps for a 383 with 30lb injectors with a 306 cam and 290cfm heads (435 rwhp) and for my current solid roller 383 at 468 rwhp right now with a slightly rich tuneup. i can send a few maps to you if you think it will help.

 

Yes, please do. I just ordered a wideband and I think if your map is close at all I could take it from there.

My email is mgm at everestkc dot net.

 

I just realized that I have two posts that are really about the same problem so I deleted the other one. Here it is:

I'm really getting disgusted by this whole situation, and I'm }{<- THIS close to selling all this crap and buying a carb. For what I've spent on this thing I could have a Hogans sheetmetal intake and two Braswell carbs.

My setup: 357" sbc, DFI 6, MSD pro billet dist with bronze gear, Pro Topline 200cc alum heads, comp xr288HR cam, Comp pro magnum pushrods, comp R lifters, SVO 36# injectors, BBK58mm, Holley Stealth Ram, 1.6 Crane rockers with guide plates, hooker LT, NGK FR5, etc etc etc...

The oldest of these parts have 50 miles on them.

The car is gutless (maybe 250hp), revs like a stock 267 (and makes similar power) with a blown accellerater pump, and everything I've tried does nothing to help. It starts right up, idles fine, and sounds great at idle and the O2 readings at idle are right at 14.7 on the narrow band with about 1-2% O2 correction. It's at least 150hp less than what it should be, based on what similar setups have made. I just don't know how it could be lacking that much in the tune up.

It pops through the intake under rapid tps increase, which would seem to indicate a lean condition, but increasing the MAP enrichment to max doesn't help, increasing tps enrichment doesn't help. The only way to make it stop popping is to fatten the base map to the point that it runs pig rich. If you do that, it revs slowly without popping, and makes enough power to run low 14's. Leaning it up to where the narrow band O2 reads correctly causes it to pop through the intake

Compression on #1 and #2 cylinders is 185 and 190# respectively, leakdown is below measurable level. I've adjusted the lifters a dozen times and it's at 1/8th past pushrod dragging right now. I've made a couple logs if that helps any.

I have the EMIC manual and have followed the step-by-step instructions for setup several times. I'm out of ideas, and would love to hear whatever advice you guys may have.

Thanks for reading all that!

 

you need a WIDEBAND. narrowband O2s are worthless on big cammed cars as far as tuning goes. Once you tune it with a wideband, then you can setup the DFI to maintain this tune in a closed loop enviroment. I think your missing power has to do with poor fuel and timing maps.

 

I'm working on buying a wideband with a logger right now. If I could somehow determine that the tune is keeping it from making the 450 or so bhp I think it should be, then I'd be happy to pay the $500 for a local tuner shop to dial it in. What I'm afraid of is that they will get into it and discover it needs twice that or more, like every other problem I've had. I wonder if I'm not throwing good money after bad.

Is there a source on the net for established calmap files?

 

you need to disable the o2 at idle speed. it is reading extra oxygen in the exhaust from too much cam overlap.so the dfi thinks its lean and keeps adding fuel but can never solve the prob. my car smokes like a steel factory if i use the o2 at idle. in the global settings you can turn the o2 on and off and also you can set the temp and high low closed loop settings. set them so you only have o2 above idle speeds say 1500 rpms. you will have to tune your idle the old fashioned way, by looking at the plugs and by the sound and the vacuum. the o2 is not made for big cams,but it will work for cruising speeds at light loads, it needs to shut off at anything more than half throttle. also whats your timing set at around idle speeds? i run 31 deg. at idle. big cams need more timing and run richer than 14.7 at an idle. one last thing, check your vacuum for leaks and use a gauge with at least 12" of hose off the intake. if your good there use the vacuum gauge to get the highest reading at idle by fuel and espec. timing. you will see big changes in vac. when you play with your idle timing. i will send you some maps tomorrow, but they are for 30lb injectors, so they it will be rich for you. if you have the time, you can figure the diff. out and lean my whole map to work for you. i cant remember, but an emic should know the figure to correct for different size injectors.

lastly, listen to tripintaz, get a wide band! its cheaper than paying for a bogus tune from somebody and the guessing about your tune up will dissapear! i have the dyno jet wide band commander (www.widebandcommander.com), and i love it, check it out, its about $500, alittle more than the LM1, but it is nicer i think and has some better features

 

The car idles like a dream. It's the only point in the operating range where it does. I'm going to order one of these widebands tomorrow. Talked to a guy tonight that has one. $279 complete and it will log to a laptop. It also displays a couple other parameters.

http://www.zeitronix.com/index.html