Inlet manifold problems.
Discussion
Can anybody shed any light on my problem?
I am part of Strathclyde formula student team, recently we have converted a Honda CBR600 FX form carbs to injection.
last week it was on a rolling road dyno to have the ecu maps tuned. Apparently when the throttle was fully opened the inlet manifold blew off with lots of flames, and i think a clean set of overalls for the dude.
he said this happens every time its opened up.
We have four injectors one in each runner into the head from the plenum(plenim......?) chamber, it seems the ecu sets them all open at the same time (open as each valve opens) this dosent seem right to me but thats what we have. we are also have wasted sparks.
We had it running in our lab and there was no probs but it only ran idle for less than a minute.
does anyone have any idea why this horrible problem might be happening, and/or any ideas how we can prevent it from happening altogether?
I am part of Strathclyde formula student team, recently we have converted a Honda CBR600 FX form carbs to injection.
last week it was on a rolling road dyno to have the ecu maps tuned. Apparently when the throttle was fully opened the inlet manifold blew off with lots of flames, and i think a clean set of overalls for the dude.
he said this happens every time its opened up.
We have four injectors one in each runner into the head from the plenum(plenim......?) chamber, it seems the ecu sets them all open at the same time (open as each valve opens) this dosent seem right to me but thats what we have. we are also have wasted sparks.
We had it running in our lab and there was no probs but it only ran idle for less than a minute.
does anyone have any idea why this horrible problem might be happening, and/or any ideas how we can prevent it from happening altogether?
It certainly sounds like the manifold is full of fuel. check your fuel pressure isn't over spec also as you're on wasted spark it doesn't take much to set things alight where a single spark system wouldn't run at all.
Check your cam timing and the position of speed sensors/ trigger discs which can introduce a large ignition timing offset if incorrectly bolted up.
Matt
Check your cam timing and the position of speed sensors/ trigger discs which can introduce a large ignition timing offset if incorrectly bolted up.
Matt
we have only got a crank sensor and throttle sensor, plus the usual lambda, air pressure and temp, water temp sensors. we had to make a new spider wheel thing with more fingers on the crank sensor.
am i right in thinking fuel pressure is set by the regulator, does the ecu have any say on the fuel pressure?
we had the engne running fine on the carbs, suggests the valve timing is acceptable. Could it be that the valves are not seated propperly?
we got the ecu from DTA i think so should it matter that all the injectors open at the same time? or does this just reduce the fuel efficiency?
am i right in thinking fuel pressure is set by the regulator, does the ecu have any say on the fuel pressure?
we had the engne running fine on the carbs, suggests the valve timing is acceptable. Could it be that the valves are not seated propperly?
we got the ecu from DTA i think so should it matter that all the injectors open at the same time? or does this just reduce the fuel efficiency?
No offence, but you seem to have jumped in at the deep-end without researching into it too much. You should know fore sure that the engine is in good mechanical order, before doing such a swap.
First off, I'd check the cam timing. Id also do a compression check on the engine, after establishing the cam timing is in fact correct.
Check your TDC reference on the trigger wheel does relate to TDC ( after setting the ecu's reference timing )
The missing tooth, should be at least 10deg before the max advance you will ever need.
So if you want 40deg BTDC, then the missing tooth on the trigger wheel must be positioned at a minimum of 50deg BTDC, with your ecu told that 50deg is where the missing toooth is located, so it knows where TDC is.
The injectors on your setup will be batch fired, they can be all together, or in pairs.
What sort of ign timing are you trying to run at idle ??
Do you have any method of monitoring AFR's ??
Start with low values on the fuelling, increasing until the engine actually runs, and idles. At least it will give you a good base to work from, without flooding or fouling plugs.
First off, I'd check the cam timing. Id also do a compression check on the engine, after establishing the cam timing is in fact correct.
Check your TDC reference on the trigger wheel does relate to TDC ( after setting the ecu's reference timing )
The missing tooth, should be at least 10deg before the max advance you will ever need.
So if you want 40deg BTDC, then the missing tooth on the trigger wheel must be positioned at a minimum of 50deg BTDC, with your ecu told that 50deg is where the missing toooth is located, so it knows where TDC is.
The injectors on your setup will be batch fired, they can be all together, or in pairs.
What sort of ign timing are you trying to run at idle ??
Do you have any method of monitoring AFR's ??
Start with low values on the fuelling, increasing until the engine actually runs, and idles. At least it will give you a good base to work from, without flooding or fouling plugs.
OK
Fuel pressure is set by the mechanical regulator if the return line ( if present) is blocked than this will raise the pressure. The ECU cannot effect fuel pressure (usually).
You say that you had to make another 'spider thingy' which I'm presuming is the toothed wheel for crank speed into the ECU, it should have a missing tooth to determine top dead centre for the ECU. The positioning of the missing tooth relative to the crank angle is critical, this parameter may be adjustable in the ECU - check where it should be.
If it was running OK on carbs and the cam timing hasn't been touched since then that'll be OK.
The injectors can fire all at once depending on how your system is configured the engine should run OK like this -indeed many early 90's cars run like this its known as 'batch fired'.
What sort of fuel mix and spark advance are you running when the explosion happens?
Matt
Fuel pressure is set by the mechanical regulator if the return line ( if present) is blocked than this will raise the pressure. The ECU cannot effect fuel pressure (usually).
You say that you had to make another 'spider thingy' which I'm presuming is the toothed wheel for crank speed into the ECU, it should have a missing tooth to determine top dead centre for the ECU. The positioning of the missing tooth relative to the crank angle is critical, this parameter may be adjustable in the ECU - check where it should be.
If it was running OK on carbs and the cam timing hasn't been touched since then that'll be OK.
The injectors can fire all at once depending on how your system is configured the engine should run OK like this -indeed many early 90's cars run like this its known as 'batch fired'.
What sort of fuel mix and spark advance are you running when the explosion happens?
Matt
the whole thing has been heavily developed and researched(not by myself) as a 4th year project. the new toothed wheel is the same gap as the original from the engine, the new ecu needs more fingers but the first and last are on the same geometry relative to the crank.
The crank sensor is also the ignition pulse generator.
does the ignition timing need to be different for carbs and injection? we have the ecu plugged into a laptop and i assume tdc is correctly set. is it best to just get a basic map and fiddle it for better performance, or is it possible to get them anywhere on the net? i dont know any of the fuel mix or spark timings.
the car is with a guy who is supposed to know what he's doing, but im not too sure that he does.
The crank sensor is also the ignition pulse generator.
does the ignition timing need to be different for carbs and injection? we have the ecu plugged into a laptop and i assume tdc is correctly set. is it best to just get a basic map and fiddle it for better performance, or is it possible to get them anywhere on the net? i dont know any of the fuel mix or spark timings.
the car is with a guy who is supposed to know what he's doing, but im not too sure that he does.
Injectors have a capacity they can flow. If the engine does not need the fuel the injectors can provide, you will overfuel and have a lot of fuel in the inlet manifold. Perhaps try to lower the times (miliseconds) the injectors are activated. It is a long shot, but with a laptop connected... perhaps worth a try.
Rob
Rob
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