I have been interested in carbs for while now and a few rescent posts have made the wheels in my head turn again. I am curious though, when running a carbed set up, how do you guys control ignition timing. A few things that I am aware of.
-a vaccum advance dizzy.
The problem that i see with this is that the ideal ignition map may not advance in a linear manner, so that you wouldnt take full advantage of timing with the rising rate of the vaccum advance dizzy.
-get a msd set up to run a set timing map.
This makes sense and I see how it would work simmilar to a stand alone so that you'd tune the fuel on the carbs and the ignition on the msd unit.

One thing that did interest me greatly however that i would like to know about is a rescent comment Bisi made regarding his "old street set up." He wrote of leaving the injector clips hanging and just using the carbs to tune fuel. In order to get over the problem with the timing retard due to limp mode he notched the dizzy to advance for it. This seemed very interesting to me. I am curious though, will there not be a lower rev limit due to limp mode, on top of very conservative timing? Anyone have any imput on this?

thank you
marcin.


Modified by dvious hatchie at 8:08 PM 12/16/2003

 

any help would be greatly appreciated.
thanks.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by dvious hatchie &raquo;</TD></TR><TR><TD CLASS="quote">I am curious though, will there not be a lower rev limit due to limp mode, on top of very conservative timing? Anyone have any imput on this? </TD></TR></TABLE>

the rev limit on a honda ecu is a fuel cut. But its not doing fuel anymore remember. It's the carb jets doing the fueling.

 

holy chit, your absolutely right!
i did not think of it at all. Thank you.
Do you know off the top of your head if the ignition maps continue on up? and also, how can you compensate for the limp mode retard of ignition?

thankyou so much.
m.

 

like u said, bisi cut his distributor post so he could advance the timing more then stock would let him. he did this so hed have a static advanced timing of a specific amount, because the ecu would retard the timing. he uses the msd for start retard (easier starts).

there are diff methods. bisi's is just simple and effective.

You can get timing units made from msd and others which let u set up a timing curve to follow. Electromotive has pricier distributor-less set ups.

SSworks (japanese tuner), uses FCR carbs on some of their cars, and I've learned from some Rcrew members their way of getting around the timing issue. they unplug the injectors, iac, iat. but they keep the tps plugged into the harness, but its rigged at WOT all the time. the map sensor also reads vacuum from one of the runners. although they have cel's, they say the timing isnt drastically effected, and u still retain the use of some of the timing map.

I will try both methods by early january (hopefully).

 

awsome info.
It definetly makes sense to notch the dizzy to get back to stock base timing. However, the problem that I found talking to a ecu programer guy is that the limp maps are not scaled or retarded versions or the base maps but rather some very conserivative maps. Furthermore, there is a early fuel cut that comes up. It is possible that with the use of the map and tps, this may be averted. I honestly dont know. Now the MAP is going to be necessary to work the ignition maps, since thats how the ecu calculates the timing.
It is interesting how SSworks seems to get around this. I wonder if using the MAP and TPS at WOT allow them to have stock maps after a certain point....

Great info, lets keep it up!

D.