Exploding Intake!...help!

[hopkid]

Yes, our intake keeps exploding... not just small back fires, but rather large explosions that send it flying off the motor(flanges and T-clamps). We at first thought is was the fuel system wired improperly, fix that, and still the problem exists. I understand that too early of an advance can also cause combustion in the intake. We have been playing w/ the timing and it does not seem to make a difference. The explosion occurs during starting, before the motor is even running. Once it happened while just cycling the fuel pump (that was before the wiring was fixed).

Does anyone have any advice? We are running a PE ECU and I was wondering if the batch fire was possibly causing a rich enviroment in the runners/plenum. We are also running a 2004, yamaha R6. Does anyone have some timing figures they wouldn't mind sharing?

Thanks in advance!

-Dave

[hopkid]

Yes, our intake keeps exploding... not just small back fires, but rather large explosions that send it flying off the motor(flanges and T-clamps). We at first thought is was the fuel system wired improperly, fix that, and still the problem exists. I understand that too early of an advance can also cause combustion in the intake. We have been playing w/ the timing and it does not seem to make a difference. The explosion occurs during starting, before the motor is even running. Once it happened while just cycling the fuel pump (that was before the wiring was fixed).

Does anyone have any advice? We are running a PE ECU and I was wondering if the batch fire was possibly causing a rich enviroment in the runners/plenum. We are also running a 2004, yamaha R6. Does anyone have some timing figures they wouldn't mind sharing?

Thanks in advance!

-Dave

[Bill Kunst]

Hey Dave-
Sounds like some 4th of july work down at UNH. I am going to state the obvious first. A typical four cylinder has either a 1342 or 1243 firing order, mess up the ignition firing and you could have the current excitment that you have now. Fuel system firing order, while important, should not cause the pains that you are having. Think of a carb (pain in itself), and there is no injection order except all the time. That being said, check your ignition order, fast, no fuel, and make sure of this.

Next problem- this is a tricky one and will get you if you think faster than your sleepless mind will process data. If you have the wrong crank trigger values(teeth, angle before tdc cylinder 1, etc) put into the computers program, ignition could be off drastically, or even constantly changing. this is not good and should be fixed before there is engine damage.

Finally, advance would be in the mid 40's at high end of operating spectrum, if I remember correctly, but idle should be less advance than this (20's or less?). Have someone verify this who has run this engine, just ask them for initial timing so that they don't feel like they are giving away their engine map.

Some questions for you to help others help you:
what trigger tooth count are you working with and what angle BTDC cylinder 1? What is your firing order? What initial timing are you throwing at it? Is this a junk yard engine (possible smashed valves)? Are you getting any firings through the exhaust, or all through the intake? Answering these questions will help.

Bill

P.S. Good luck.

[Jersey Tom]

Holy shit. Well that's not good. I'm no engine guy, but here is my line of thought..

Since you asked about timing.. at low RPM (idle-ish) AFAIK for a sport bike motor you shouldn't need more than 15 degrees advance. High RPM (redline-ish) 35-ish.

That said, I don't think that matters, unless you're running like over 90 degrees advance, which is ridiculous anyway. The plug should be sparking at the end of the compression stroke, ya? The intake stroke should have been done with long ago, intake valves shut long ago. Should be no way of the combustion in your cylinder to be going back into your intake.

So that leaves me to one of two possible conclusions. One being the intake valve(s) of one or more cylinders isn't seating and sealing properly, so the combustion can fire back into the intake manifold. Or, your injectors/plugs are connected in the wrong order and/or the firing order is set wrong in your ECU. In that case, instead of the correct cylinder firing right before the end of the compression stroke, its firing right before the bottom of the intake stroke, while gas is being sprayed in there and the intake valves open.

[Bill Kunst]

I guess Tom and I were writing at the same time, but I looked with the search and found that Brian Lewis of PE LTD. suggests 10-20 degrees advance for start and idle for most engines. Give it a try, but I would recommend looking into trying it without the intake on, or with a blastgate on the thing.
Bill

[Superfast Matt McCoy]

We had our intake explode about a week ago. We hypothesized that it was because our throttle was completely closed (total seal, not even cracked for idle) and so it just created a vacuum in the intake and sucked the fuel back into the intake during valve overlap. We set the idle screw on the throttle plate and haven't had the problem since.

[Superfast Matt McCoy]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> The plug should be sparking at the end of the compression stroke, ya? The intake stroke should have been done with long ago, intake valves shut long ago. Should be no way of the combustion in your cylinder to be going back into your intake. </div></BLOCKQUOTE>

PE is a wasted spark system. it sparks not only at the end of compresson, but also during overlap. We had a lexan intake cover for our dyno intake (note: bad idea) and looking down the runners you could see the spark plug going off on the wasted spark during cranking.

[VFR750R]

Are you running 4 coils or 2. If 4 are you sending a single every 360 or 720 degrees. If you are sparking during overlap...that'll do it.

[LSU Dave]

Man, yesterday was not a good day for cars with the PE http://fsae.com/groupee_common/emoticons/icon_wink.gif Had mine blow up too for the first time. Thankfully it should only happen when you get a ton of vapor buildup in the intake like I had by screwing around with the injectors. I just need to be more careful next time! Thankfully I didn't have the intake bolted down or the single small crack could have a been much more drastic.

Yes, I actually blew the welds on the intake manifold. - "You almost had me? You never had me - you never had your car... Granny shiftin' not double clutchin' like you should. You're lucky that hundred shot of NOS didn't blow the welds on the intake! Now me and the mad scientist gotta rip apart the block, and replace the piston rings you fried."

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by hopkid:
Yes, our intake keeps exploding... not just small back fires, but rather large explosions that send it flying off the motor(flanges and T-clamps). We at first thought is was the fuel system wired improperly, fix that, and still the problem exists. I understand that too early of an advance can also cause combustion in the intake. We have been playing w/ the timing and it does not seem to make a difference. The explosion occurs during starting, before the motor is even running. Once it happened while just cycling the fuel pump (that was before the wiring was fixed).

Does anyone have any advice? We are running a PE ECU and I was wondering if the batch fire was possibly causing a rich enviroment in the runners/plenum. We are also running a 2004, yamaha R6. Does anyone have some timing figures they wouldn't mind sharing?

Thanks in advance!

-Dave </div></BLOCKQUOTE>

[Garbo]

In 2004, when I was at Memorial, we ran a 2000 R6 with the PE. I seem to remember about 15-20 deg advance at start, 40-ish at redline. We started with the generic 4-cyl motorcycle map on their website, trimmed out some fuel and gave it more advance. Check your trigger wheel with a timing light, we had back/front fire issues before doing this, fixed it and it ran first go from the downloaded map.

Cheers
Garbo

[Garbo]

You've probably already seen these but maybe not...

http://www.pe-ltd.com/Downloads/Yamaha%20App.pdf

http://www.pe-ltd.com/downloads.htm

For the map, look at the bottom of the downloads page.

[B Lewis @ PE Engine Management]

Hi Guys,

The wasted spark firing arrangement can potentially lead to backfires until you have the start-up fueling ironed out. Also, try adjusting the starting compensations, specifically the priming pulse. Using this feature provides more fuel during the first revolution which helps the engine start quickly. It also reduces the possibility of a lean burning mixture during starting. Lean mixtures tend to take longer to burn completelty, increasing the chance that combustion is still occuring during the exhaust stroke. Also, you can contact us if you have any specific questions. Good luck all!!

[Chris Boyden]

Stock R6's run 55 degrees advance all in by 5500 rpm. At least the 99' R6 we ran in '03 did. It's in the service manual.

We ended up taking it to 60 degrees BTDC. No problems. That was with a TEC3 wasted spark setup.

Seems like a lot, but don't be scared. With the PE, you'd have to advance the timing wheel
one notch to extend the advance, which (please correct me Brian) is ~11 degrees per notch. The PE is limited to 50 degrees total advance based on reference pulses. Advance one notch, and you've got 11 degrees minimum at idle up to 61 degrees total. Proper timing really brings these guys to life.

[VFR750R]

That's probably a load sensitive spark map. It will read 55deg on the stand, where the throttle position is maybe 8% to get 5500rpm, but at WOT I doubt there is 55 deg. Suzuki's are even spark timing adjusted for what gear your in, in addition to throttle position.

[JuicedH22]

As has just been said, your problem is because of the high fuel vapor that builds up in the plenum when the engine isnt running (you will have that during the early tuning process) it usually only happens during start up because the vaccum clears the plenum while running. It can occasionally happen while running if overly rich while tuning, this problem is even more pronounced if you have short runners. All of this mixed with the wasted spark means that when you go to start the engine, you ignite a cylinder w/ an open intake valve and therefore ignite the vapor in the intake.

You can do a few things to help prevent this during tuning. After you kill the engine, open the throttle and clear the vapor before you start again.

Another thing that will make this even more of a problem is if you have your coils wired wrong. Are you wired in parallel or series?

BTW, i speak from experience, I have personally had a throttle body shoot off of our intake and drill me in the chest when one of the guys helping me tune decided to test fire the coils while i was working on the TPS....

[Chuck Dean]

Another factor is intake design. We have had the exaxt same problem with one of our itakes. It had poor injector placement (caused fuel puddling on runner and had short curved runners that let to a plenum. The orientation of the plenum was such that suspended fuel vapors could puddle there as well.

So, after the engine has been running, if you wait a little bit and let that residual fuel mix in the intake/intake port, an explosive air/fuel mixture forms in the intake.

However, there shouldn't be an ignition source with the intake valves open unless you are getting sync errors and igniting the coils at the wrong time.

[hopkid]

My theory is exactly as explained above by JuicedH22... I just don't understand how it is happening so much. Granted this is my first year tuning. I will try harder with the starting compensation and definately blow out the intake between starts. I can remember one time the intake came clear off and left all four intake ports flaming... indicating some really wet ports. Are runners are definately short which coincides w/ what JuicedH22 said.

I have checked the wiring, banks and batches (2&2). We are running less than 10deg BTDC total advance for starting (I think i'll advance this).. and quickly rising to 50deg by about 6000rpm. Also, to answer a few other question, firing order is 1243, it is batch fire so theres a spark every 360 (which doesn't help). The injectors are wired parrallel, coils in series.

One other question. When we turn the exhaust fan on in the dyno room which create a vacum in the exhaust, one of the head pressure release valves (I thought they were just head breathers), leaks. It will pull air through. I thought these were only one way valves designed release head pressure from the cam turning. How could this be linked to the exhaust? Is the air slipping through a valve guide of an open valve? This doesn't happen w/ the engine running. I thought it was kind of strange. Maybe a bad seal?

Thank you again for all of your help... back to the dyno room!

[BeaverGuy]

Those are clean air valves. They are part of the emmisions systme and pull air into the exhaust. There is a small hole that runs down from the reed valve to the exhaust ports. We have always capped them off in some manner.

[Stupid Freshman]

is that intake tightened down enough dave? sounds like a stupid question, but an easy solution

[Manas]

is ur intake exploding right from the very beginning? or is the phenomenon intermittent ?

if it's the latter, better Re-check as per the previous replies to the post.

BUT,
If it is the prior and NOTHING mentioned till now in the thread seems to wrk, better check out your timing chain & / or tensioner .

the valves might be playing games due to faulty timing chain/tensioner.

this is the ONLY reason ,except for those already mentioned, that i could think of which explains the problem u're facing.

[magicweed]

Just came from it running. Isn't exploding as far as I can see, and this is after taking into account all the previous suggestions. Runs like a champ under light loads, but getting it on a local chassis dyno seems to be the next logical step. It's getting a little down to the wire.

[awhittle]

50% of all fuel problems are electrical
50% of all electrical problems are fuel
When things are screwed up, look at the last thing you did.
When thing are realy bad its two things that is causing it, no one thing could do this.

The first thing I would look for is an ignition system that is taking several rotations of the crankshaft before it is correctly finding the cranks location. A work-around is cranking the motor with the ignition operating and then activate the fuel injectors. On my setup I have a way to make the cranking PW 30% longer for the first start of the day.

Hope this helps

Andy