What is the problem?

Pokageek

Pokageek

Active Member
Jun 10, 2005
2,767
0
46
MA, USA
#1
Hi guys. I have a lul from 2000-2500 rpm :notnice: and there is a 100rwtq climb from 2500rpm to 3000rpm. I go from 300rwtq to 400rwtq...in 500 rpm!! :shrug: It seems a bit too radical a jump for the car and sometimes it pops. I drive this range all day and it gets on my nerves a bit. It wasn't this way right after I had the long tubes on IIRC. It was smoother with No dip in it.. So what is the problem? My tuner said he shut off the 02 sensors so it will idle right and I don't remember it being this way right AFTER I had them put on. My a/f is perfect and they cant find anything wrong and say its just the radical cam. I am getting 20mpg which is strange in a 500+HP car.

LT Headers AFR 205's
2000 rpm=310rwtq
2250 rpm=280rwtq
2500 rpm=305rwtq
3000 rpm=400rwtq
the rest of the curve its over 400rwtq until 5600rpm

Shorties AFR 205's
2000 rpm=280rwtq
2250 rpm=300rwtq
2500 rpm=325rwtq
3000 rpm=340rwtq
3750 rpm=400rwtq
the rest of the curve is above 400rwtq until 5200 rpm

Shorties Pro-Comps
2000 rpm=325rwtq
2250 rpm=340rwtq
2500 rpm=360rwtq
3000 rpm=370rwtq
4000 rpm=400rwtq
the rest of the curve is above 400rwtq until 4300rpm then straight down
 
#5
Last time I went 181 miles it was on 11.5 gallons. You must do all highway driving or don't romp on it much. Personally, I have to hit 6 grand at least once every time I drive it. :D

I don't really have any help to offer on your problem. Popping usually means it's lean I think. Mine would do the before I had it tuned, but I think it was because of bad O2 sensors. I changed them right before having it tuned and seemed to run a lot better.
 
#6
THIS KINDA THING! ... Boys and Girls ... Is where datalogging is KING :Word:

You would wanna duplicate the driving condition while gathering data

You would then adjust the various tables based upon the data you saw
to make things more favorable

Just like Velveeta :banana: ... Easy Cheezee !!!

Again ... Hard Data ... It has no opinion and it don't lie :nice:

I can only guess :shrug:

Did he kill the O2's just at idle or what :shrug:

Are you just easing into the throttle or going to the floor?

never the less ... The data should tell you what is needed ;)

Grady
 
#7
Speaking of that, is there a way to data log without a tweecer? I was looking into different self tuning methods a couple weeks ago and didn't really find anything for OBD I datalogging, everything is for 96+ OBD II. :notnice:

Since I already have a SCT chip, I was looking at the SCT Pro Racers Package. It comes with the software and chip burner for around $700 ( :eek: ), but I couldn't find any way to data log with it. If there was a way to pull the tune from my SCT and transfer to a tweecer chip, that's something I might be interested in doing...


Back on topic, I think I see what Grady is getting at.... Could the dip in power be caused by the O2's kicking on/off? I know a friend of mine has a weird dip on his dyno charts that he says is something to do with the PMS tuner. Maybe something about the injectors since he's using 55# or some odd # like that.
 
#8
Thanks Grady. It does that when I am easing the throttle. Its ever so slight but is still there. LT's added a ton of power overall though. When I got 20 mpg I was flooring it a few times and driving 100mph from PA to lower part of MD late at night with no cars. No kidding.
 
#9
Low-5.0 said:
Speaking of that, is there a way to data log without a tweecer? I was looking into different self tuning methods a couple weeks ago and didn't really find anything for OBD I datalogging, everything is for 96+ OBD II. :notnice:

Since I already have a SCT chip, I was looking at the SCT Pro Racers Package. It comes with the software and chip burner for around $700 ( :eek: ), but I couldn't find any way to data log with it. If there was a way to pull the tune from my SCT and transfer to a tweecer chip, that's something I might be interested in doing...


Back on topic, I think I see what Grady is getting at.... Could the dip in power be caused by the O2's kicking on/off? I know a friend of mine has a weird dip on his dyno charts that he says is something to do with the PMS tuner. Maybe something about the injectors since he's using 55# or some odd # like that.
Click to expand...

Well Mr. Mike :D

It won't take long for me to exhaust my knowledge about datalogging
if using interfaces other than the Tweecer method :(

I do know PMS can datalog but it requires additional software

I do know SCT can as well but have no specific knowledge
but
I do know for certain, Don 95GT has addressed the issue in past threads :nice:
so
It wouldn't be too hard to find the straight scoop :)

Grady
 
#10
Pokageek said:
Thanks Grady. It does that when I am easing the throttle. Its ever so slight but is still there. LT's added a ton of power overall though. When I got 20 mpg I was flooring it a few times and driving 100mph from PA to lower part of MD late at night with no cars. No kidding.
Click to expand...

Hey Keith

I can only make a WAG here :shrug:
but
The info you provided makes me wanna think along these lines :D

Since you say it happens when you ease on the skinny pedal
and
When you are at a very low rpm

The issue has to be occuring under a light load ;)

With a combo such as yours ... you could have these kinda things going
on when driving at a light load

The spark could be quite high
The fuel could be fairly fat due to the big inj's

Then ... you said he killed the O2's to get it to idle better
so
You'd be getting no help from the pcm's adaptive strategy :(

I can say I had to do the same due to my narrow 109 lsa cam :bang:
and
I did have to do a bit of tweecing to make it all play nice together :crazy:

Like Mike said above, it could be a transition thing :)

You know ... the O2's are not smoothly coming back in place

Little issues such as this is where a general knowledge of how the pcm
does its thing can be such a B I G advantage :Word:

I once had a similar problem of a nasty lean spike when I would go from
a light load, almost closed throttle, to a WOT condition

I tried + and - of fuel/spark with no success :chair:

Then I found the answer while searching the various tuning forums :banana:

Work with the plenum size of the upper intake ... Problem solved :spot:

Just a random thought or two ... I guess :shrug:

Good Luck with finding the problem :nice:

Grady
 
#11
Thanks Grady for the help. My AF is perfect according to the tuner. Its not too bad but the car was smoother and had more low end in that range with the shorties.

I am selling my short block and going TURBO 393 anyway. I will probably sell the accufabs lt and 3" mid pipe anyway. Thanks for the help guys. If I were to keep the engine I would go PMS or somtehing or go back to shorties.
 
#12
Pokageek said:
Thanks Grady for the help. My AF is perfect according to the tuner. Its not too bad but the car was smoother and had more low end in that range with the shorties.

I am selling my short block and going TURBO 393 anyway. I will probably sell the accufabs lt and 3" mid pipe anyway. Thanks for the help guys. If I were to keep the engine I would go PMS or somtehing or go back to shorties.
Click to expand...

Always glad to try and help a fellow :SNSign: Stanger :D

I'd be willing to bet the biggest steak in Fort Worth, Texas :)

You could make that bad boy behave as you wish within the Tune :nice:

I'd certainly go that route before hosing around with parts and such ;)

Good Luck with the new combo :nice:

Grady
 
#13
Pokageek said:
Thanks Grady for the help. My AF is perfect according to the tuner. Its not too bad but the car was smoother and had more low end in that range with the shorties.

I am selling my short block and going TURBO 393 anyway. I will probably sell the accufabs lt and 3" mid pipe anyway. Thanks for the help guys. If I were to keep the engine I would go PMS or somtehing or go back to shorties.
Click to expand...

Haha, I was just thinking about doing the same thing. You may want to look into going with a smaller CI, like 360-370 range. The problem with big strokers is they move a ton of air, too much for smaller turbos. If you're going with a huge turbo and lots of boost it shouldn't be a problem.

I'm just repeating what I've read here, so I could be wrong. Don @ Lasota posted that (or something similar) a while ago.
 
#14
The Zeitronix ZT-2 wideband may be just want you want for logging as it will take in quite a few valuable inputs: Wide Band Air Fuel Ratio Meter

SCT doesn't provide anything for logging EEC-IV. twEECer is king for logging on these cars, I would just be guessing trying to tune without one, especially on the CBAZA cars. BinaryEditor/twEECer combo really kicks some tail. Add in a DataQ to log AFR/Boost/Fuel Pressure and you have a kicking little setup priced very competitively. Give me a shout if you want to discuss PRP and other options in more detail.

Wes
 
#16
LOL. Sure Chris. I have 3.55 gears, my spedo is prolly 3 mph fast IF that - which I dont think 3mph would affect much. :shrug: Does it? Yes my odometer is accurate.

The tuner even said I must be getting great gas mileage with my AF, what ever that means. Now here's something different. My trans is a 5 speed and I had a special 5th gear put in at a .64 ratio.
 
#18
Thought I'd jump in here real quick :D

The thing about our Hot Rods that is kinda shocking :shock:

They can get pretty reasonable gas mileage ......
on the highway at steady cruise at a reasonable speed ;)

But

Driving around town :shrug:

Who builds a ... Hot Rod ... To Drive it like their Grandmaw :Word:

Then ... You get the opportunity to see :eek:

Those "Big Ole Injectors"... They really can pass a lot of fuel :rlaugh:

Grady
 
#19
Well Chris, I decided I have really turned tis thing into a monster. I dont want a rumblin shakinn, no cat stinky bucking vehicle. I want a quieter, smoother, non-smelly Lightening speed car. SO I am going for it. :)
 
#20
UPDATE: Ok, I disconnected the battery last night because I was fixing the rear window power motor thingy... I went out to drive it today after taking my panhard bar off and NO MORE HESITATION! It is the dam computer adjusting to my LT's again. Sheesh, I just need to find a tuner to tune it out. Amazing that the puter is learning a strategy that I dont want. At least I know what it was.
 
You must log in or register to reply here.
Top Bottom
Back
Forums
Menu