Michael Filippello

hello, i had a thread sometime back about a problem i was having regarding a stumble that occured when my car went from primary to pri+sec inj operation. some of you may remeber this thread. well i never was able to fix this problem. i am now hoping that i will be able to tune this stumble out using the datalogit and software. i just ordered my datalogit and should receive it within a couple weeks time. after reading the electronic manual at yahoo groups, i noticed that there are more settings accessible via fc-edit than are available with the fc-commander that deal with pri. to sec. inj transition. i am looking to see if anyone already running the datalogit might be inclined to post all the related #'s that deal with injector settings, such as pri/sec transition %threshold, pri/sec overlap, lag times, etc. i can then use the info i get from you guys and compare it to what ray programmed in with the power excel software. i did not have this problem before i upgraded to the 1200cc injectors and sent my pfc back to ray for the retune. i have gone round and round and have not been able to isolate the problem. i will give a detailed explanation of what is happening along with my cars particulars for reference.

when i was running the stock injectors, i did not have a stumble. i bought my power fc from sr motorsports and he tuned it for my mods. i put it in and all was good. i noticed down the road that i was almost maxing out my stock inj. i finally got up the money and gumption to change the secondaries out for 1300cc units. ray offered free reprogramming if i got the inj. from him so the deal was on. when i got everything back, i put it all in and went for a test drive. i immediately noticed a stumble that was not there before. i talked to ray and he told me some things to check. it was not fuel pressure, it was not bad inj. o rings. it was not a cut vacuum line. nothing i checked proved to be bad. i sent the computer back to ray along with the 1300cc inj. for him to test. he said all check out fine but that he was going to send me brand new 1200cc inj. instead of my upgraded used 850's. he hoped this might help. it did not. i finally gave up on the problem and just drove the car. the stumble always occurs when the sec. inj. first come online. there is a lean spot right at the transition point which is confirmed by my o2 sensor readings dropping into the teens for a split second and then recovering. it is not rpm dependent and is not the 3k hesitation of old. i can not find any mechanical reason or fault. this is why i think it might lie in the programming. if anyone has any insight into this i would appreciate all the advice or suggestions i can get. like i said earlier in this absurdly long post i would like some programming #'s to have for reference also.

my car is as follows:
93 touring manual
power fc with commander
street ported motor, ported upper and lower intake manifolds, port matched gaskets. polished intake plumbing and exhaust manifold, upgraded sequential turbos with t25 exhaust wheels and super 60 trim compressor wheels, front mount greddy intercooler,dp/mp/pfs cat back, cold air intake, crane ignition, magnecore wires, ngk plugs (all 9's) 550pri and 1200 sec. inj underdrive pulleys(not that that matters)

hope this helps and hope i can finally get rid of this damn stumble. thanks in advance to everyone who is willing to help

ps. anyone try the antilag yet :-)

atihun

Have you added more fuel to those cells where you see the stumble?

atihun

-double post-

atihun

-triple post- damint slow forum!

Michael Filippello

it doesn't happen in any one area. it might happen at 6ooo rpm or it might happen at 2000 rpm. the only constant is that it always happes when the secondaries come online. if i am in 1st gear and accelerate slowly, i can extend the use of the primaries all the way into the upper rpm band. as soon as the computer decides it's time to switch to pri+sec, i get the stumble. if i am in 3rd gear and start to make a moderate pull the need to go from pri to pri+sec happens at a much lower rpm do to more boost asociated with the increased load of being in 3rd gear. then the stumble may happen at 2500. since fuel requirement is a combination of many different things(rpm,boost,load,temp,tps position,and others) it never happens in a specific spot. i have used a volt meter to watch o2 readings and put my fc commander on inj duty map in order to see exactly where the dip occurs. as i drive around, everytime i acceleate to the point where the sec. come on line that is where the volt meter readings drop and the car hicups. the readings immediately recover and all is fine. if i jump on it from a low rpm you don't notice it because the car is dumping so much fuel so fast that the transition gets masked. it is mostly a problem on light to moderate accel when the inj duty cycles are climbing moderately and not steeply like when you just floor it. the only time you notice it when you floor it is when you are in a situation that you are in high rpm's but are still only using the primary inj. for fuel. in this situation, as soon as you give it more gas the car needs much more fuel and being this high in the rpm band means you were on the threshold of going to secondaries anyway. so you get the stumble. after you shift and keep it floored you don't notice anything. i feel that electronically the sec inj. are not firing as soon as they should and this is creating a small hole in the overall fuel delivery. i have my lag set to +.04 as everyone else. i don't think it is the harness because it happened as soon as i went to the bigger sec. then again maybe messing with the ends disturbed something i can not see. is there any way to check the harness to see if that is the problem. to just replace the harness is very expensive if it is not the problem. thanks again

adax

iTrader: (2)

You could try this once you get your Datalogit:

Change the lag time of the secondaries to 0.20 this is what RC Engineering told me was appropriate (can do this without datalogit).

Leave Pri/Sec transition % alone. This relates to when transition occurs. Wade Lanham has an excellent post regarding this somewhere.

Change sec transition from 1.5 to 1.06
This is the starting pulsewidth of the secondaries (I think) and needs to change when secondary size is changed. 1.06 = 1.5 * 850/1200

I'm not sure what injector overlap is. XS had mine set higher than the base mod map and it stumbled bad at transition. It's now set like the base mod map (1,2,and 3 as I recall)

Once you get your Datalogit, look for a post on the group about stumbling. Others have delt with the same problems and resolved it as above.

Alan

rynberg

I know you state that it's not a fuel pressure issue, but you don't list an upgraded fuel pump in your list of mods. I apologize if you already have tried this, but I didn't read through your previous post.

Michael Filippello

your correct, i forgot to mention the upgraded fuel pump. i have the one from sr motorsports. the drop in nipendenso one. i received some emails from some people that said that i am not the only one that has this problem and that most likely the fix will come from adjusting some settings that are available through the datalogit. i just sent my money today. i also just bought a used hp laptop. next is the wideband. does it ever end man. i will have over $2500 in computer related mods alone. i could go to europe for that much:-) then again no rx-7's over there.

rx7tt95

I too have a bit of a stumble. I use the 1300's and SR tuning btw...but my stumble is usually only at low revs when I mash it, say in 4th at 1.5 or 2K. And then it's only momentary. I think it's "muted" somewhat everywhere else in the rpm range. I'll have to look at my settings when I get my Datalogit up and running on the Mac. Perhaps it is something Ray is entering.
Michel

Michael Filippello

ok everybody who is listening, i finally solved my dreaded stumble problem

the promblem was in the programming as i suspected. i did not have access to this area until now. my datalogit just arrived it was the inj. overlap settings that did the trick. i tried messing with the sec. transition (ms) setting and this did not help my situation. i read on the datalogit site that this # should be changed to 1.06 for 1200cc inj. this only seemed to make things worse for me. my stumble was from a lean spot not a rich spot. lowering this # meant even less fuel. for those of you out there like me who see a drop in o2 voltage when the secondaries come online, you may want to leave this # at 1.50

what i did was to increase the inj. overlap #'s. instead of 1,2,3 from the bottom up i put in 4,7,7 from the bottom up. this immediately removed my stumble. my o2 graph now looks almost flat through the transition. i am going to play with the #'s and see if i can get it perfect. it is now 95% there. you know i have to go for 100%. wold you guys accept anything less.

today is a good day. i would like to thank someone from the datalogit group for suggesting this. if anyone has any questions i will be happy to try and help.

mike

spyfish007

Mike: Thanks for the info. Did you log the inj pulse width for the primaries and the secondaries? I'm going to go try it. Also did you test this out with and without the transition time changed? I've noticed that injectors seem to work different than the datalogit guys suggest but I'm not 100% on that one yet. The parameters I'm talking about are in the advanced section. Looks like I'm going for a quick drive. I'll post more when I get back.

cewrx7r1

iTrader: (2)

It would be interesting to know how many have had this problem with or without having the PFC retuned for larger secondaries when their size is still within the commander size range.

I am non-seq and went to 1200s with only changing the size with the commander. Mine has worked perfectly.
A seq turbo friend has done the same change and his also works perfectly.

From posts on this forum, it seems the problem occurs when either the secondaries are larger than 1200, someone reprogrammed the PFC for the larger secondaries, or the engine has large ports and or large single turbo.

Michael Filippello

Hey Carson, i logged the inj. duty cycle in the basic section in one chart and the o2 voltage on a second chart directly below the 1st chart. every time the duty cycle would drop during accel. there was that dip in o2 voltage. it would recover and go back to normal. after changing these settings the dip was basically gone. there is still the slightest dip but it is not noticable by the seat of the pants. i am going to play with the #'s and pay more attention to accelerating at the different boost levels outlined in the overlap box. i assume the programming interpolates for areas between the 3 that you can set up. i will go for a test drive this weekend and set the #'s one by one to find the optimal #'s for my car.

Chuck, you are right. some people have this problem and others don't. i can not figure it out either. I am one of the people who had their Ecu reprogrammed by Ray when i purchased the larger secondaries from him. The weird thing is that i don't see any changes that he made other than to make the lag .04 and put in 1200 instead of 850. he did not change the the (ms) for the secondary start up or the 40% transition point. by the way, i did increase the 40% to 50%. this alone made no change in the stumble before i messed with the overlap. i have not put it back at 40% but will do so to see what happens. i do not think it will make a difference. i do have extensive port work done to my car and i have enlarged stock turbos. i did however have the porting done while still using the stock inj. setup and did not have the stumble. the Turbos came at the same time. this could have something to do with it. before the swap i had the stock turbos in stock config.

i should mention that i had upgraded turbos for about 5 weeks after the engine was rebuilt. during this time i had no stumble. i was using stock injectors. after the break in time was over i starting pushing the car. about 2 weeks later the primary turbo bent a shaft. i had them rebuilt and they bent again. i decided to put the a set of stock turbos back in and shelved the upgraded ones. i drove it like this for about 6 months. no stumble to be had. then i found out about turbonetics rebuild they do for the stock turbo where they also upgrade the exhaust wheel with a t25 unit. they said no more bent shafts. i decided to try this and sent in the extra set of turbos to have them built. at the same time, i sent off the 850 inj. and the cmputer to Ray to have them upgraded and reprogramed. when i got everything back and installed, i then had the stumble. i never noticed it during the 5 weeks that i had the old upgraded turbos. even though 3 weeks were at break in and the other 2 weeks were full of regular driving, i never had the problem. unless the turbonetics units are moving more air than the old set i can not see any reason for the stumble to be caused by this alone. i am going to call Ray and discuss this with him. It is funny because the person who suggested changing the overlap got the idea after seeing one of ray's programs in which Ray changed them for a customers car. why the hell didn't he do this for me 6 months ago when i sent the injectors and computer back to him to see if there was something wrong with them.


mike

forcefed1

the more I read about the datalogit the more I figure once you buy one you are invited to a members only group to discuss problems. am I correct or is there a discussion group for the datalogit I can join without owning one?

Michael Filippello

you have to buy one before you can be invited into the discussion group. most of the people in the group are also on this forum so you can usually get all the answers to your questions here as well. most of the things that you miss out on are the dat. files for programs and emails about why something is not working for a particular person. i highly recommend buying the product. it has already solved this one major problem for me and is worth every penny i paid for it


mike

twokrx7

iTrader: (1)

I also had a stumble at transition with my ported motor and single turbo. I also increased the overlap and it appeared to help. I noticed that XS does this as well.

Funny you mentioned that Ray had programmed another PFC with increased overlap, he did not have the Excel software before, maybe he now has a datalogit???

SPOautos

This is totally off the subject but I have a unusual question about your car. I'm going to start collecting some data about the stock turbo's bending shafts and had a questions for you.

What kind of bov do you run? Is it stock or aftermarket? How much boost had you been running when the shaft bent?

Also, so I can contribute a little to the subject. I run 1200's and never had a stumble problem. Mine was tuned by xs.

Thanks,
STEPHEN

Michael Filippello

Hello Stephen, i am running both the stock BOV and a Greddy type s located on the pipe that goes from the turbo outlet to the inlet side of the intercooler. the 1st time i bent the shaft i was just running the stock BOV and (12psi). the guy who built the turbos said he would rebuild them but that i had to buy the greddy from him or he wouldn't waranty them next time. we put the new BOV and the rebuilt turbos back in. 2 weeks later the primary turbo went again (12psi). this time we just put some stock ones back in with a little flow work done on them. they worked perfect. i could definately feel the loss of performance however.

I now have the ones from turbonetics. no bent shaft yet but lots of problems with leaking seals and smoking. i had to send them back 3 times. The 1st time they leaked externally from the rear turbo, between the bearing housing and the exhaust housing. sent them back and then they smoked all the time. sent them back again and now they only smoke when i start the car untill the seals heat up is what i am guessing. they still have a small leak that sometimes gives off that burnt oil smell around the car. it is hard to smell over the rich fuel smell that is also always around the car

hope this helps
mike

to keep on topic, which turbo are you running on your car? is it a single? also what settings are you using in the overlap area? i would like to compare.

spyfish007

I'm running 50% for secondaries transistion, @ 0.76 transition time, and 5,7,9 for my injector overlap and things are getting smoother. I also too some fuel out of the accelerator map--I'm single with 1680 injectors. All of this is making the car run better. I am still way too rich in many areas-but progressing nicely.

Michael Filippello

Hey Carson, I am also running 50% transition. I left the time at 1.5 however. Have you noticed any difference in smoothness by lowering this #? i couldn't tell so i put it back to stock. The overlap #'s definately helped. Now that the stumble is gone, i plan on taking the car to the dyno. they have a wideband, so i can tune it in. Any suggestions on how to best utilize the logging functions to make the propper changes. I am assuming that the dyno will chart hp and air fuel vs. rpm. What is the best way to log so that i know where to make changes after the pull?

mike