fstfwd

iTrader: (1)

Hey guys... I have been trying to troubleshoot a problem with my car bucking at high boost levels (running 99-jspec twins sequentially). I have a Power FC and was wondering if anyone in the Connecticut area would be willing to loan/rent/offer their Datalogit for a few hours, or weekend... so I can just do some runs and see what the hell is going on. It would be great to get some data while these problems occur (which I can only seem to reproduce on the open road) and hopefully get some useful information to pinpoint the problem.

I have been wrestling with this issue for a long time... many trips to the shop, and we haven't nailed it down yet. We've swapped out BOVs, installed manual boost controller... it was happening prior to the new 99 twins... so it shouldn't be them... check EVERY hose on several occasions... the list goes on. It really makes "racing" er umm... driving spiritedly not fun at all.

Would be willing to offer large quanties of beer... or whatever suits ya... I just don't have the means at this time to spend $400 on a Datalogit. Maybe some day.

I know there are a lot of good people on here... so I hope someone will be able to help me out. Willing to drive into New York or lower Mass on a weekend if that would work better.

Thanks!
Steve

Tim Benton

iTrader: (1)

explain the bucking...WOT at 5K and above, part throttle, etc. Does it jerk sort of like the 3K hesitation with the stock ecu? Checked the ignition side of it? new plugs, wires, etc? What about the fuel pump, is it upgraded? Changed the fuel filter out lately?

Tim

fstfwd

iTrader: (1)

Example situation... I'm cruising at 4k rpms... 3rd gear... I push the peddle to the floor... run the boost up to 14lbs (set to max at 15) car starts to jerk and buck and the boost studders, and I basically lose acceleration. If I ease my foot off the gas a little... I can hold the boost at 12 or 13lbs... and the car will keep accelerating fine.

The fuel pump and filter have only about 10k on them... plugs are fairly new... and the problem has occured for quite some time now (back when those parts were "newer").

I have been reading a post which suggests that it could be the Throttle Positioning Sensor. Upon further discussion with a friend of mine, we are encourage that it could have something to do with it based on the facts. I am not a mechanic, and I may be making wrong conclusions... but this is what I am wondering (from a laymans perspective).

If the TPS isn't calibrated correctly, it is sending wrong voltages to the ECU. The ECU controls the boost and fuel, et such... based on that. My friend, who has quite a bit of electronics knowledge, suggests that if the TPS is out of range, e.g. above 5volts... it might register a voltage of 0v. Which the ECU would interpret as if my foot had been taken off the gas and let the boost out and cut the fuel. Thus causing the studder/buck. But then the ECu suddenly realizes that my foot is still on the throttle and kicks the boost back in and so on... the cycle continues and it's a bucking Bronco.

So I was hoping the Datalogit would make it easier to monitor these values. But if I can't get my hands on one of these... we will have to do some manual observations with a volt meter... even use my Power FC sensor check... which is hard to follow - especially when you are bucking all over the place.

fstfwd

iTrader: (1)

^

RotorJoe

Post your mods.

Sounds almost like break up.

When I had ign. break up on mine. I was able to go WOT at 10psi, but not @14-15psi. If I did WOT @ 14ps it would sputter and fall on it's face. Lots of black smoke out the tail and you could smell fuel. If you only stayed just ahead of the cars acceration with the throttle it would run much better and may not fall on its face. An ign. amp fixed all that.

I think if the TPS was out of spec you may have more issues with idle then you do at cruse or WOT (someone correct me if I am off in left field on this one).

The whole post was just a thought?

fstfwd

iTrader: (1)

Thanks x605... that basically describes what I have been experiencing. If I go WOT, the boost just breaks apart -studdering and bucking the car at 14-15psi... but if I ease my foot off just slightly... down to 12-13 psi...it will hold. Really a pain if you are trying to get max boost while also keeping your eye on the road.

Here are the mechanical mods on the car...

Street port 1.3L Rotary engine
'99 J-Spec twin turbos
1300cc secondary injectors
Racing Fuel pump
Manual Boost controller (tried to bipass stock solinoids to see if that would help)
A'PEXi Power FC ECU
A'PEXi Dual intake system
A'PEXi Twin Chamber BOV
Greddy Intercooler
Koyo Radiator
ACT Street Clutch
Straight downpipe
Tanabe Racing Medalion Exhaust

I appreciate your help.

cabaynes

iTrader: (4)

sounds like you need to get tuned by a professional

RotorJoe

Do you have a WB 02 Sensor? Do you know what your A/Fs are?

When did this problem first happen? Was if after a mod/upgrade?

Just getting more back ground to try to help.

Thanks

fstfwd

iTrader: (1)

No prob x605... I appreciate the help. I don't have a WB 02 sensor... but I have monitor the A/F volts in the Power FC (at WOT ~ .92volts) and have a crappy Autometer AF gauge which shows I may be running a little rich... but as far as I can tell not Lean.

It's been persisting for quite sometime now (almost 2 years)... it is hard to tell when exactly it happened - related to a specific mod. It may have started when we put the 99 turbos on the car... or it could have been happening before. I was focused on a different issue at the time and it was a while ago. We thought another boost issue was related to my stock turbos so I upgrade to the 99 J-spec and the problem didn't go away.

As a result of upgrading to the 99's, it seemed like the break up was more apparent. Dave at KD Rotary does all the work and his initial explaination was that because the 99's spool up so fast, the stock 93 solinoids can't keep up with the boost, and cause the gate to open up. Though, if this was just an issue of losing boost or not producing enough boost to get past 14psi... that would be one thing. But it's causing my whole car to buck and twitch and not accelerate and it's embarrasing and frustrating.

The other boost issue we have been trying to trouble shoot may or may not be related to this. In a nut shell. I can boost on/off all day long if I don't kick in the second turbo (staying below 4500rpm). When I rev the rpms past ~4300 or so, the sec turbo kicks in and I accelerate nicely... maintain boost (until it breaks up) and all is well. The bad thing happens when i take my foot off the gas... and most noticable on the highway... when I go to hit the gas again, I get NO boost. The car just moans - and if I eak 1lb out... I'm lucky. So I try to get the RPMs below ~4300... and that seems to help a little... and if I keep my foot on the gas... regardless of gear... after 5-10, or even sometimes 30 secodns, it will suddenly spool right back up again!!

But, like I said, this may not be related, or it might. Dave spent most of his time trouble shooting this issue... checking hoses... putting in a manual boost controller... checking solinoids... we went through a lot of stuff. Thought we had "improved" the situation... but it just plain doesn't like me. I could almost deal with that problem more than the break up.

Does this help at all?

Thanks.

RotorJoe

Wow, sounds a lot like what I was going through. I wasn't sure if I had a boost leak, boost control problem, or ignition break up.

When I bought the car the owner said he had a boost leak. He was right and I replaced many of the hoses. I was able to determine that it was not a boost leak problem any more due to the fact that I could build full boost at lower RPMs and then at higher RPMs the car fall on its face.

I then thought it was a problem with the PFC and boost control. While doing my homework I found out that my boost was controlled by the external HKS controller I have on my car (I can't help you with the duty cycles of the PFC boost control). I made that thing relearn the boost curve but I still had issues.

I then installed a WB 02 sensor and saw that my 02 ratios were (or are) at about 10.5:1 at 12 psi and up. I then did lots of searching on break up and found that I may have that problem. What helped to clue me into this were my mods on the car and the fact that the previous owner took out an amp on the upgraded coil.

There were two things I could have done at this point. Because I had the datalogit and WB I could have started pulling fuel out. But I trusted the tuning job and was scared to take out fuel. So I bought an HKS amp, which runs both coils (leading and trailing). The previous one that came with the car (but removed) was the Jacobs which amps the leading coil only.

I went out and found that it was break up and the amp fixed it.

That was my story in a nutshell. Your problem sounds similar but could be something else. I am not suggesting you buy and amp until you know for sure (hate to waste money). Sounds like you could have boost control issues still. Although it sounds like you have hunted down that path pretty extensively.

It may be break up. I know people say you can make 500 hp (maybe a touch less) with the stock ignition, but I cannot. I like my car to run eye-bleeding rich, its safer.

You need a WB 02 the stock 02 with a gauge is not accurate enough. Mine would (I have a NB and WB gauges hooked up) and still does read .93 or so under boost. That is rich but impossible to tell what A/F ratio is.

Am I correct in thinking you have no mods to your ignition?
What about upgrading to BUR9s all the way around. (Helped me a bit before the amp)
Do you know someone who will let you borrow their amp for a test drive?
Who tuned your PFC or what map are you running?

Mods listed below
Sorry about the length.

fstfwd

iTrader: (1)

Thanks for the detailed response... that is another encouraging possibility. I haven't done any mods to the iginition. KDR in PA tuned my car... but not recently. Certainly something I should look into. The last time I took the car down there, the dyno was broken so I couldnt' have it done.

Are BUR9s wires? I'm not sure if anyone in my area has an amp I could try out. I'm in Milford CT so if anyone local is reading this and can help, let me know. I probably could head down to KDR and Dave would throw one in just to test. He actually suggested I get one a while ago - but not as a solution to this ... more like - "okay dave... what should I install next"- hehe.

I just want to try to narrow this down as much as posssible... and either fix it myself, or have Dave jump in on it and maybe throw in an amp - and dyno the thing with a WB O2.

RotorJoe

BUR9s are spark plugs. You probably have 9s in the trailing side and 7s in the leading side. The 9s are a "colder" plug. They are able to pull more heat out of the combustion chamber. Many people run 9s all the way around (I do) and others (who produce more then 400hp or so) sometimes run 10s. These are to help hinder detonation. I don't think this is your problem but it has helped other cars run smoother and idle better.

Good Luck and take it slow.
http://www.ngksparkplugs.com/techinf...000&country=US

fstfwd

iTrader: (1)

Thanks x605... I appreciate your thoughts. Definitely something I will seriously consider looking into.

Steve

fstfwd

iTrader: (1)

^

GUITARJUNKIE28

i was having a similar problem with a car i was tuning a few weeks ago. it would fall flat on its face @ about 1 bar...turns out the wastegate spring was 1bar+...i believe it was fuel/ignition cut or whatever the pfc uses...i didn't look into that part too closely. he's getting a lighter spring and we'll be doing it again to check the results..

does your pfc use the stock map sensor, or is it configured for 3 bar? what's the boost level set at? maybe you could try turning it down just a bit and see if that helps?

IGY

What is your boost set at in the pfc? Even when you don't use the pfc to control boost, the boost control settings still trigger a boost cut at .2kilo over the setting. So, if you have the boost settings on .8 and you are trying to hit 15psi the computer is going to kick in the boost limiter(fuel cut).

GUITARJUNKIE28

^ much better explanation of what i was getting at.

Jason

iTrader: (5)

Sounds to me like its ignition breakup. Get a twin power or something similar, run all 9 plugs and it should clear the problem up.

Jason

fstfwd

iTrader: (1)

Hmmm... wastegate is another possibility. The boost was set using the power fc to 12lbs and 15lbs. We eliminated the PFC (for bosot) with a manual boost controler. I've been meaning to test the car with the manual boost control set to stock (all the way tighten the adjustment screw), and see if that causes any break up. one of those "obvious" things that I probably should have done.

I am still using the stop Map sensor... to the best of our knowledge it is working properly.

Just out of curiosity... how does the wastegate spring and fuel cut relate to eachother? Just trying to clarify your example. Thanks!

Steve

fstfwd

iTrader: (1)

(err, I meant stock Map sensor)

Good point about the PFC boost settings... they certainly could be initiating a fuel cut. I tried changing the setting to the 12lbs (actually, I think it might be 10lbs) and it still let me run up to almost 1 bar before it broke up - BAD.

So I tried to turn my manual boost control down this morning on the way to work. I tightened it all the way so that it would basically run stock boost levels. To my alarming surprise, it had little or no effect on my boost levels. Which didn't used to be the case. So I go under the hood and then it became clear. A few months ago I brought the car to Mazda, simply to have them remove the UIM so that I could polish it. When they were re-assembling everything the mechanic there saw a vacuum hose that was capped off, around where my intake is. Being the "helpful" guy, he spent quite a bit of time (which they tried to charge me for) looking for where it attached and put it back on. I am thinking that this was an integral part in making the Manual boost control work. So they F@#$'d it up.

This pisses me off, because I really wanted to see if this break up would occur at stock boost levels. I have a TurboXS Manual Type Boost Controller. Does anyone know of a particular hose that needs to be capped off inorder for this to work. This way I can bring it back to Mazda - tell them what he needs to fix, since I'm sure he forgot. And I sure as hell not going to pay for it. Arg!

I appreciate your feedback guys... this is very helpful.

matty

i dont think its ignition break up...i have break up and i must say it doesnt sound as bad as what you are describing. I will go for a ride with you soon.
How about being too much fuel? Do u see black smoke when this occurs? what are your inj duty cycles? One fast alternative is to bring to pruven and run it on the dyno...see what your afr;s are when this happens. Atleast you will get some feedback as to your mix.

fstfwd

iTrader: (1)

Hey matty... good to see you got my message - hehe. Yeah, the car is runnig a little rich.. I haven't noticed if my car is smoking or not. I'll take a look at the duty cycles when I go home later. I'm in the process of writing Dave at KDR a long note. Maybe we can fix this once and for all.

RotorJoe

I still think it is break up too.

But make sure your boost settings in the PFC are set by .2 over (1.4Bar, PRI and SEC) what your target boost is. This is to avoid fuel cut.

matty

break up is hesitation.....what he is saying is the car falls on its face. He isnt that far off of stock where his car is having that much break up....he said wires and plugs are new/er.

fstfwd

iTrader: (1)

Yeah - I'm not exactly sure what meaning breakup and "falling on its face" means among different users. But the sensation in the car would be as if I abruptly popped my foot completely off the gas... and then almost immediately when back to WOT. Like someone trying to learn how to drive standard. Hehe. But at 5500rpms and 14lbs... this is a real jerky mess!

While I was driving the car home from work yesterday... I was messing with the boost settings - I honestly think that jerk at Mazda completely disabled my manual boost controler and reconnected the Power FC to the solinoid. Thanks for nothing! So the mbc all the way down does nothing.