PLEASE HELP! Bike dies after hard pull

Tmoney21

Registered
Hey I have a 2006 hayabusa engine in a sandrail. I recently got the sandrail back from a tuner in Las Vegas NV. Neither they nor I have come across the solution to our problem.

We can "putt" around all day and part throttle stuff but as soon as we do a nice hard pull and let off the throttle the AFR immediately gets LEAN and the motor dies without returning to idle. Then after it dies the motor will not start up and idle or perform normally unless you let it sit for 5-10 minutes then it will run perfectly fine until another hard or semi hard pull.

Does anyone have a clue what I can even suspect or check out or anything? We are kindof at a loss. The motor is turboed running around 8psi boost. Low compression pistons forged rods and cross cut trans. Garrett g28 turbo. The fuel pump is sufficient I will get details on it tomorrow.

What could cause this to happen?

I am at a loss and I haven't been able to go out and play with this thing for months now. We need some help!!!!
 
1. What kind of tuning system are you running?

2. Anything abnormal about the tuning system? Anything custom with the sensors or are you running all Suzuki sensors to feed back to the management system?

3. While we're at it, tell me a little about your fuel system, what kind of a regulator are you running and do you have a fuel pressure gauge?

4. Does it finish the hard pull clean and as soon as you let off the throttle the engine cannot recover, or does it start to stumble or quit when you're still on the gas?
 
Because the way it sounds when I'm first reading, it could be a multitude of things. Anything from the fuel regulator malfunctioning, a sensor going out of range and needing a little time to 'reset,' etc. I hate diagnosing **** like this over the internet, phone, just not being there in person because it seems I have the strangest effing problems myself, but they're not too bad to work through when it's actually in front of you.

I wouldn't be too frustrated at this point though, it's a problem that is easy to repeat which makes it 10,000x better/easier.
 
1. What kind of tuning system are you running?

2. Anything abnormal about the tuning system? Anything custom with the sensors or are you running all Suzuki sensors to feed back to the management system?

3. While we're at it, tell me a little about your fuel system, what kind of a regulator are you running and do you have a fuel pressure gauge?

4. Does it finish the hard pull clean and as soon as you let off the throttle the engine cannot recover, or does it start to stumble or quit when you're still on the gas?


First off thanks for your response!

1. The tuning system is a PCV I have the autotune modual but its dissabled and only used for AFR readings currently.

2. Nothing should be abnormal I plugged it in the same way I would in a the bike. There are some modifications to the engine harness from Tom Pro himself whose been doing hundreds of these cars and hasen't had this issue yet. The modifications basically include deleting the gauge cluster and deleting the turn signals. The gauges I have are still ran off the ecu so I don't think its irreversible.

3. Fuel system is sufficient. The tuner said hes made over 700hp in an evo with the same fuel pump. It is a bosch 044 or 254 or something like that. We are unsure of the fuel filter being a fuel injected filter but it ran fine on the same filter when I first purchased this machine. Its got a rising rate FMU from BEGI i believe its the begi 2025. It does have a fuel pressure gauge and fuel pressure stays in the green when the sandrail dies. (Add) It does have bigger injectors too. They are a modified Bosch injector about 65% bigger than stock, also the secondary rail and injectors are dormant no controller for them and no need with the modified primaries.

4. It will finish the hard pull clean but then as soon as you let the throttle off the engine doesnt recover and then it wont start back up normally. You can get it to start and keep it running but you need like 1/2 throttle and it blips around 4k rpm but as soon as you try to let off the throttle it will die then like I said you can keep it running just have to do massive blips upwards of 4k rpm. Will not even try to idle.
 
Pictures!!!!!! =]

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Sweet buggy. Hope you get it figured out. If I knew anything about turbos or even motors for that matter I would chime in.
 
Thanks man! Yeah Its a shame it cant be used I need to figure this shizz out. Im thinking back a bit one of the injector plugs was bad and I "fixed" it but it was never perfect. I wonder if as it revs up and starts workin if it burns out the contact for a bit... I think I will replace that injector harness and see if it changes anything... But it did run the way it is now for a few dune trips... Any advice is appreciated guys and ideas something I can check out deeper or any logical reason it is doing what its doing. Thanks in advance!
 
So fuel pressure is normal, it goes lean after a hard pull, no real trickery in the wiring or the sensors.

Bah, I was kind of hoping you were going to say you had a Megasquirt on there or something, this kind of makes it harder because I don't think they have much of a data logger (never really played too much with Power Commander stuff).

Without poking at it first hand, hearing it, being able to really be in front of it, it sounds either sensor, ECU, or (long shot) injector related.

I would drop it off with the tuner at this point because there are loads of questions and checks that can be done in half an hour that would takes us days and days to get through and the tuner knows almost all this stuff already. It's just a matter of checking to make sure the inputs are all reading correctly, the outputs are being output, and you're right, the only thing I can think of that could be a mechanical issue would be the injectors.

Thing is, you can normally run and limp around on 3 cylinders, it will die but it doesn't require half throttle to maintain an idle. If an injector is simply sticking closed because it's getting too hot, getting beyond its duty cycle and needing time to cool (which is entirely possible), you could see this simply by running it at full throttle, letting this issue occur once again, have a friend start the buggy and hold it so it runs while you check the temperature of each header primary with a heat gun (obviously the cold one will show you which injector is having the issue). Then you simply swap that injector with another one, do the pull again and if the cold primary follows the injector you moved, it's an injector problem.

Really good looking rail though, I love the 1 and 2 seater rails and can only imagine how much of a blast they are. You'll get this figured out and it probably wont end up being too bad. Remember, check the injectors like I said and swap them around, use that heat gun. Also sensor inputs and injector outputs, should tell you the issue plain as day.

Good luck!

P.S.
As much weird **** as I've seen, I've never seen a consistent problem like this that was caused by wires or contacts. Don't rule it out, but at first glance I would say you were probably safe in that area.
 
It's an electronic fuel starvation problem in my estimation. Get it tuned by a Busa turbo tuner. My guess is that your FMU is cutting off fuel after boost. Running lean isn't good either, motor wont last. Check your A/F, but a good tuner will find the problem. Good luck.

P.
 
I see the problem... the engine is not in the right frame... put it in a bike frame and see if that does the trick... JK, SWEET ASS BUGGY!!! Good luck bro!
 
Are you by chance running the stock tip over sensor? Incorrectly positioned (or malfunctioning), it can shut the fuel pump down and cause some of the same issues I see in your thread. Looks like you checked a lot of other things, so I thought I would throw a dumb guess your way . . .:whistle:
 
Nice rail! I can't offer any help since I'm clueless about turbos :stoopid:
 
This thing was at the tuners for 3 weeks >< He told me when I left it was a physical something not giving fuel to the engine. His suggestion was the fuel tank was getting vacuumed and starving the rail after a hard pull. I told him simply to pull the fuel cap off and see. He made excuses for not pulling the cap off so I took it as he didn't know what was causing this after 3 weeks of "tuning" it.

The thing that makes it hard to diagnose for me is that it will come down from rpm and stop idling but then it will not start right back up without half throttle and blipping it around 4k rpm as soon as you let off the throttle at all its dead again. But the factor time here is that if you let it sit for an X amount of time then try to start it you have no problems...

So that time is either letting something cool down or what else could be happening in that amount of time for it to be able to return to a "normal" state and start running like a champ again?
 
I assume when it dies it will still turn over it just wont start.....?
 
I did use the check valve yes, and yes it turns over and will start but only if you give it half throttle and keep it high in the rpm.. It will not idle or act normal until you let it sit.
 
Have you checked the TPS(throttle position sensor) to make sure it is not loose or a wire shorted from it to the ECU?
 
I think the TPS is fine it reads right on the power commander software. If it was faulty would it really cause it to not start back up again?
 
Any other suggestions? I am taking it out either tomorrow or saturday to do some testing. Going to put the old fuel pressure reg on there. (no more FMU) I am going to install the new injector plugs I got just to eliminate my possibly bad "fix" previously. Any other suggestions though? Run it without the fuel cap on?
 
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