The TOAD Prince and the 3 SRT wishes

And what is your first wish fellow toad “Waldig”

Well your greatness, I would like to keep my car from going Lean at high Boost.

Schzaam DING!

Great, I don’t have a lean problem anymore? Terrific Thank-You.

Gee this is great, HEY WAIT A MINUTE my car went from 17
: 1 all the way to 10 : 1, that’s too rich now!! Can I get my wish back or get partial credit or do I have to use another wish????

Well it’s the way that it is. I added a boost line to the fuel pressure regulator and it worked, just too much. Lets examine the problem, the car goes lean at elevated boost levels. This is due to poor delivery of fuel from the injector in part due to depressed differential pressure. Adding pressure to the fuel rail assists the injector to deliver enough fuel, but this must be controlled so that we don’t add too much.

Most cars ( mine ) are ok in the F/A arena up to some pressure like my 18 PSIG threshold. I DO NOT need to not add fuel much before that, this becomes apparent looking in the rearview mirror; it all makes sense, NOW.

So far the following has been determined:

1 Boost control of the fuel rail pressure can overcome lean out under boost.

2 Bigger injectors do not seem to be needed for our engine

3 Our fuel pressure regulator is capable of adjustment with a boost “signal”.

4 Operation above 20 PSIG boost is possible with the existing fuel pump and injector set-up.

5 Further development is needed to provide a Working solution, though the progress seems promising.

6 The boost signal is a sledge hammer effect AT THIS POINT
I have included a data logger screen for a run with the boost controlling the fuel pressure. As you can see the F/A is often 10:1 which is Trump rich and in need of attention.

The Code 3 pulley will be added and tested before I change anything to see how “over 20 PSIG operation” looks. Also I what to find out what is the max boost attainable with stacked pulleys.

This is a project in process and I am reporting the ups and downs for the general enlighten and technical information. Its been interesting; but to be useful, the boost modification of the fuel regulator needs
better control.

The data logger shows the F/A being real rich as the fuel pressure is being raised from 60 up to about 72 psig. The vertical line shows the F/A rising to about 13 and a boost of almost 20 PSIG Boost.
Be Happy, Woody

 

Great testing Woody, you may be on to a soulution that helps me as well.

What is the outside air temperature and are you logging it to see the difference it makes? Im assuming you are, as you dont seem to forget many variables.

Im especially interested in seeing what difference increased boost(20-22psi) makes and especially in cold weather (35-50 degrees).

ps, your hitting 19.70 psi with your 178 mm pulley it must be COLD there. Why does it show TPS is only 90% open?

 

How consistent is this mod?

At first impression, it sounds like we should do the fuel mod, and then carefully lean out the ECU tables to compensate so it is not as rich.

However if the fuel mod fluctuates results depending on variables(weather, for instance), then it would seem to risky to lean the ECU out so much as to compensate.


Ideas?

 

Woody, thank you very much for your Testing and sharing the datalogs with us!! What would be also interesting is a datalog from the TIMING-Advance Curve and how the IATs respond to driving under boost. I wish you all the best and good luck with your testing!!

 

I was thinking that same thing last night when I read this. Get the extra fuel there with this mod then tune it where you want it. As you said though, it needs to be a somewhat consistant increase, or else it wouldn't work.

 

+1 that seems to be the right idea. Good thing he can datalog his runs. Temps are crucial, and everyone who is thinking of this solution needs to get a datalogger. That way you will have the option of fine tuning your ecu to compensate with your temp variables. Great DA will produce more boost.