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Discussion in 'SN95 4.6L Mustang Tech' started by ADRENLN, Jul 19, 2008.
i have cats on my car so i think i need them all but i could be wrong.
the rears are not needed. they just let the comp know if the cats are working....that is their only function. turn them off in the tune
You have to have the front o2 sensors on any FI car.
I have Autometer Cobalt Wideband gauges and it came with Bosch O2 sensors. Everytime I start my car, the gauges counts backwards from 20. That is because it's heating up the 02 sensor to get proper readings before the gauge starts. I don't remember what gauges you use or if this info really means anything at all but just figured I'd throw it out there. Just trying to help when I can. Good luck man.
I have been researching good tuning shops in my local area (in Central FL), and came across Justin @ VMP Tuning. He really knows what he is talking about, and I'm definately taking my car to him when i get back from Iraq. One of the things he told me was to get some MotorCraft O2 Sensors before go in for the tune! He said that he has seen that other brands (such as Bosch) dont efectively heat like they should, and it can cause issues. Just a bit of info he passed to me (that I didnt know) so I figured I would pass to you... I hope all goes well! I know how frustrating it can be to have an issue that you just cant figure out, and to have the shop tell you "ya, thats all i can do"! See my "Help with tuning(?) issue" post for my story...Lol... Once again, best of luck!
thanks guys! also, i had new bosch 02's in there from the first builder who put everything together. the new shop took them out and i had to buy the ford ones. so that is probably part of the problem.
well, my new tuner says that the sct tuning fixed the current proble. however, there is a new one hes trying to get to the bottom of. @ around 5500 rpm the maf signal starts to go crazy and jump up and down and all over the place making it hard for him to get an accurate air fuel reading. he says its when the boost really hits hard. however, his boost numbers are lower at this point then the other guys. he says im only making 11 or 12 psi at 5500. the old tuner told me 15...strange. anyway, i dont care about that right now however his hp numbers are about 25rwhp LOWER then the old guys right now. well hope he figures it out then we will see what this ting makes.
dont forget its the new abaco meter blowthrough. i guess its just no one has experiance with it too much yet.
ill keep you guys updated.
where is your BOV located??
11-12 psi sounds about right. i'm only seeing 18 with a 2.75 pulley and a 10% OD at 6500 rpm
ITS DOWN BY THE DRIVERS SIDE FENDER.
he cant figure out why the everything gets crazy in the upper rpm. he thinks it might be the meter. so he wants to switch that to sct too but then i have to get an sct and tubing to make it fit cause its different then the abaco, and then he needs to tune again even to see if that is the problem. im just out of cash.
right now it sits at 500rwhp @ 6000 rpm but the a/f is unstable at that level. that is with less timing in the tune. he wont put the full tune together with about 2 more degrees of timing until we get the upper a/f issues and the crazy maf signal ironed out. i might have to just let it be for now....broke
What did I tell you about your MAF being located that close behind a bend in the tubing?
Move the meter up and your problems will go away. The air is flowing faster on the outer edge of the pipe, and the inner edge is going slower. The air is entering your meter like this and mean while just starting to try and straighten out. This causes ALOT of turbulence, and thus your wacky readings.
Here is the pic I am talking about....just imagine hurricane force winds going through that pipe, and how jacked up the air direction will be where your MAF is.
Cut your aluminum pipe about 3-4 inches, to where the back of the rubber coupling for your MAF is about 3/4-1 inch away from the IAC hose. Get another rubber elbo thats longer, or use the piece you cut off to bridge the gap with another silicon connector.
I'd get the SCT meter and have him redo your tubing.. Sell your old meter on Ebay... You are really close, dont give up now! You could always search the boards or ebay for a used SCT maf...?
im not giving up guys. i put too much into it. we were close in a sense and still far at the same time.
heres the verdict. the car is fixed of the original problem. you guys are right about the meter and how close to the bend it is. that has to be changed and it will. right now it is driving fine and im going to keep it that way for over the winter. i cant get into the boost too hard and it has timing pulled because it detonated with 15 degrees. that is a whole seperate issue i was unaware of. 14 degrees is in it now and it is ok for now..
so i called tim @ MPH who built the shortblock and ron @ fox lake who did the heads to try to find out what the compression ratio is.
well, fox says that the combustion chamber is almost the same as stock, its 45. and he takes about half of the swirl dam out. tim used 18cc pistons in the block. so im not sure where that puts the compression. tim said that it is prob. aroubd 9.2 and ron says its like stock like 9.5.
so bottom line is that is too high!!!! for 15 psi on 93 octain. so im looking for ways to bring it down.
one thing my new builder/tuner mentioned is bigger blower cams in the spring. mine are only 212-214 @050 he says to go in the 225/235 @ 050 range. he says that will lower compression.
can bigger blower cams lower compression? i guess that m y mystang will be undergoing some more changes next spring when im working again.
thanks for any info....and you guys have been a great help and have been sticking it out with me the whole way.
Shouldnt have detonation @ 15PSI and 15*s....nowhere close. You should be able to put a good 17-18PSI on that low of timing. Tims cylinder heads LOVE timing from what I hear too....very interesting.
Stock is 9.4 I believe...maybe 9.375. Man its one thing after another ....did he happen to tell you what the IAT temps where when it had knock?
He has fox lake heads, Tim built the short block. I wasnt aware that cams could change the compression ratio, but then again I dont know it all
I am glad its better! I'd love to put in some blower cams, but mine is a daily driver..
THAT seems to be the problem. tims shortblock with foxlake heads and cams. the compression is around stock. i looked at the dyno sheet and im making 14psi. do you think that 14 psi on stock compression with 15 degrees of timing should cause detonation? i didnt think so.
im not sure if a bigger cam can lower compression that is just what i was told.
im going to call tim back with the new info about foxlakes heads and see what he thinks about the compression before i go digging back into the engine with a bigger cam. i really dont want a bigger cam. my a/f seems high too. even before it goes nuts on the top end cause of the meter. ill post up later.
A bigger cam can lower boost. Maybe thats what he was thinking?
What's your fuel system setup?
just cobra pumps and #60 injectors with a kb boost a pump.
i dont know how my compression got so high! i specifically asked all the builders if the heads and block setup would work with 15 psi. thay all said id be fine. now they are telling me that my compression could be too high for the boost!!!!
so a cam will only lower boost not compression? whats the point of that? i would just rather pulley down and spend alot less cash. however, i got this set up to run 15-17 psi. i was under the impression that id be at 8.9 compression, now they are telling me it might be like stock compression after i spent 15 grand and its all together????? holy crap what am i going to do. this is not right.
hopefully there is something else wrong.......i have to call tim.
a cam shouldnt lower the static compression but it may reduce dynamic compression because of overlap. Not sure if Im using the right terms though.
No way. I ran 12.5PSI at one point on my GT, and was getting around 16*s of timing. I considered that SAFE....and it was a stock bottomend. I never heard anything out of that motor.
Your problem with detonation is also stemming from your MAF placement. With your MAF getting wacky turbulent readings like that , a nice strange little thing will happen. Since timing is based on engine LOAD and RPM....when the MAF doesnt see all the air coming in, it thinks less air is there so obviously less fuel....thus the leaning, but at the same time it bumps UP your timing due to it shifting into another load cell thats for lower airflows, and higher timing. Less air means less energy, means less heat, means the engine can accept more timing. Now with the MAF flickering around and giving false readings, your timing can jump around a pretty large amount very rapidly.
THAT combined with the leaning condition thats also caused = detonation.