13 replies to this topic

[Apdiliars250]

Hi I'm just after some ideas what is causing a misfire around 3k 4k.It feels like its hitting the rev limiter or launch control on full throttle.I can drive past that RPM fine at half throttle

I have had the car on the dyno set up in 2D because my Map sensor is not registering boost so I have ordered a dearer one.

The ignition map is retarded quite a bit around that RPM but it was fine for a couple of days after the dyno.

The ignition map... https://flic.kr/p/2pXfJrV

I tried to do a video but it's hard to hear on the video but I'm letting off when it happens.

https://youtu.be/lLc...?feature=shared

Thanks

[Apdiliars250]

I have checked the plug gaps and replaced the coil. Checked the crank sensor gap.sprayed around the carburetor and inlet manifold with carburetor cleaner and found no leaks.

[Steve220]

That map makes little sense. Is the Y axis absolute pressure? I.e 100kpa is atmosphere? The timing is very advanced!!! What is your cam and what is it timed in at?

[Apdiliars250]

The timing is running off the very bottom row.
The map sensor is switched off at the moment because it's not working correctly I have a new one to test.

It's a avonbar phase 2 cam

[Apdiliars250]

The timing is running off the very bottom row.
The map sensor is switched off at the moment because it's not working correctly I have a new one to test.

It's a avonbar phase 2 cam

[Steve220]

The revs are X axis (across the bottom). Y-axis I assume is absolute, so its not actually showing boost. Its also a 3D table, not 2D.

[timmy850]

I don't like the 0kpa line at the bottom, especially if you don't have a map sensor at the moment and you are feeding in boost. 

 

Your timing goes off a cliff from 27 degrees at 2800rpm to 15 degrees at 3500rpm.

 

27 degrees at 2800rpm, plus an unknown amount of boost sounds a bit risky

15 degrees at 3500rpm off boost would be a bit of a dog

 

From what I can tell:

0kpa = 0psi

100kpa = 14.5psi (1bar)

Does this mean you haven't got any vac advance settings available?

 

Ignition timing safe by James Rickwood, on Flickr

 

 

KPA setting from the instructions 

https://canems.co.uk...tion_manual.pdf

 Screenshot 2024-06-15 085256.png   342.13K   5 downloads

Edited by timmy850, 14 June 2024 - 10:54 PM.

[Steve220]

Yeh, that map needs a lot of work.

[Apdiliars250]

I dont have any vac advance settings. The MAP sensor was faulty and the ignition was just set to be ok to drive safer than it was.

I have a new MAP sensor now. so the ignition can be set up a lot better. im just trying to figure out if the misfire under load is the ignition map or something else. it was fine with this map for a couple of days.  

[burchy35]

I had a very similar annoying issue like this, I tested and checked everything over and over.
It ended up being the crank trigger sensor, at certain revs it must of started to vibrate causing the drop off of timing. I had dropped the alternator very low so I could fit the bigger intercooler and one of the supporting brackets for the sensor was coming from the lower part of the alternator.
I redesigned the way I mounted it and it sorted the problem. The alternator must of been causing extra vibration or interference.
Just a thought for you.
Good luck and keep at it, you will sort it.
Roy B

[Apdiliars250]

I had a very similar annoying issue like this, I tested and checked everything over and over.
It ended up being the crank trigger sensor, at certain revs it must of started to vibrate causing the drop off of timing. I had dropped the alternator very low so I could fit the bigger intercooler and one of the supporting brackets for the sensor was coming from the lower part of the alternator.
I redesigned the way I mounted it and it sorted the problem. The alternator must of been causing extra vibration or interference.
Just a thought for you.
Good luck and keep at it, you will sort it.
Roy B

I did thinkthis so I moved the sensor closer to the pully.

Cheers

[sonscar]

Personally I would not even start a booster motor with a non working map sensor,disaster can happen in seconds.Steve..

[lsto]

When mine ran like that it was over advanced under load, at part throttle it was fine, if I nailed it then it would stutter briefly then pick up again. Just for reference around that rpm at full load if I recall correctly my timing sits about 18 degrees. Why it didn't do it initially but developed it later, maybe air temp depending how efficient or if you have an IC fitted, even down to fuel could affect it.
Good luck with your map

[Apdiliars250]

Well I have solved that misfire I re-sealed the dash pot and the problem disappeared. The new MAP sensor is fitted and working.
And the ignition map is a bit better.

https://flic.kr/p/2q6kvzG