(solved) Major tach spikes @ ~4800rpm

[naprotejay]

I've been having a consistent problem with the tach/rpms spiking whenever I hit ~4800 rpm. I have not been able to *succesfully* rev above 5000 rpm so far because of this spike, resulting fuel cut, etc......

Please see attached datalog for an example of what's happening - any ideas?? Details of the install are in my sig link...... other than this rpm spike, its running very well. What could be happening???? I'm getting my tach signal from an IG- output in the oem diagnostic box.

I have a dyno scheduled for Wednesday and would like to get this figured out......Appreciate any help!!

[S.Bretz]

It looks like the signal goes bye-bye completely and then pops back up with a huge gap.

Have you tryed lowering you rpm lag average?

What is your next pulse tolarence set at normal running?

What the predictor algorithom set to?


Also check your power, ground, and especial the tach wire for good contach If you have a poor connection, the accelration and or vibrations at that rpm could cause the circuit to momentarily open.

[naprotejay]

S.Bretz thanks for the reply..... I didn't mean to ignore your post

Anyways, I found out what it was over the weekend....... I bought my MSII preassembled with the HALL sensor circuit in mind as my tach input. Well, I had been using the stock coil's *IG-* for the tach input since I initally couldn't get the HALL signal to work.....

After reading through some of the assembly instructions - which I obviously hadn't done due to taking the easy way out - I realized that to successfully use an IG- input, some different components had to be installed.....

With some more help and searching, I finally figured out how to use the HALL signal (12volt pull-up) - now I can rev right up to redline!

[rb26dett]

good to hear

fred.
Posted by email.

[naprotejay]

good to hear

fred.

thanks Fred!! even better were the dyno results yesterday: a healthy (extra) 8-10+ ftlbs from 2500rpm(!) all the way to ~7000!! Still have some fine-tuning to do with the MSII, but those are my 1st real dyno results since installing it.

[rb26dett]

8 - 10ftlbs? do you mean better than last time? i hope so   i cant even imagine driving something that slow.

Posted by email.

[naprotejay]

8 - 10ftlbs? do you mean better than last time? i hope so   i cant even imagine driving something that slow.

better than last time I'm now at 133whp / 118ftlbs but the peak numbers aren't as impressive as the curve itself. See the chart here if the attachment doesn't show that I posted above:

http://forum.miata.net/vb/showpost.php? ... stcount=29

[Bernard Fife]

Fred (rb26dett),

Sorry, I apologize for my post about not insulting other users, I realized after re-reading the original that you were referring to 8 ft-lbs being slow, which seems to be a reasonable comment. I thought you were saying this users car was slow even with the improvements - which on second look doesn't seem to be the case .

Not insulting other users is always applicable, of course, but I recognize now that this wasn't what you were doing - sorry again!

Lance.

[rb26dett]

Appology accepted (like i have a choice ;-), I have a soft spot for
older 323s (protejay in the USA). I wish him only the best, and on his
current output, with a guess at the weight of his car, I'd say his car
is faster than my skyline (rb20de powered). You wont ever catch me
doing what you thought I had done. I may be vocal and opinionated and
a little too honest, but I'm not an !@#$hole.

Perhaps we can be friends yet lance?

Regards,

Fred.

P.S. Post correctly capitalised with an attempt at punctuation as per
etiquette link in your sig.
Posted by email.