VE Analyze

[joeyb]

With Tuner Studio and Mega Log Viewer the VE Analyze will tune for a specific data log.

Will running this help adjust the pulse width on the fuel injectors after upgrading from 33lbs low z to 96lb low z? I'm planning to run the new injectors and turn up the boost - should I do a new tune each time I make one of these adjustments? Mega Squirt is also running my ignition table for COP on plug ignition.

I'm running a mix of 109 unleaded race gas and 92 techron (50/50).

Want to thing about 50/50 E93/race gas. Besides using VE Analyze to tune for the different fuel, do I need a flex fuel detector? Will the flex fuel detector allow megasquirt to automatically adjust for the amount of ethanol in my gas?

I'm focused on the injector change - the fuel is another topic (sorry). Any feedback on tuning for bigger injectors would be awesome! Thanks

[joeyb]

I gather I will have to adjust my pulse width numbers after running VE Analyze. Is this done by creating an ignition log?

[Matt Cramer]

With Tuner Studio and Mega Log Viewer the VE Analyze will tune for a specific data log.

Will running this help adjust the pulse width on the fuel injectors after upgrading from 33lbs low z to 96lb low z? I'm planning to run the new injectors and turn up the boost - should I do a new tune each time I make one of these adjustments? Mega Squirt is also running my ignition table for COP on plug ignition.

The VE table should not require retuning. All you need to do is rescale Required Fuel and injector opening time (and if using MS2, acceleration enrichment).

I'm running a mix of 109 unleaded race gas and 92 techron (50/50).

Want to thing about 50/50 E93/race gas. Besides using VE Analyze to tune for the different fuel, do I need a flex fuel detector? Will the flex fuel detector allow megasquirt to automatically adjust for the amount of ethanol in my gas?

You would want to use a flex fuel sensor if you did not run a constant percentage of fuel. If you're always running a 50/50 split, this is not needed. You will, however, need to retune your spark advance.

I gather I will have to adjust my pulse width numbers after running VE Analyze. Is this done by creating an ignition log?

Ignition logs are a special purpose log that only examine the RPM input and nothing else. They contain no pulse width, engine load, or AFR data.

[joeyb]

Thanks! I'm going to look more into the required fuel and injector opening times.

[joeyb]

Okay - so 148.2 cu engine with 96lb injectors in a 4 cyl means 4.0 Req. Fuel. What about fuel pressure? I'm running 58psi instead of 43psi.

I'm looking into the injector opening times.

[joeyb]

oh yes, it's MS3

[Matt Cramer]

Required Fuel should be calculated on the basis of what your injectors flow at the fuel pressure you are running.

[joeyb]

I've managed to get the new injectors to work out really well. I'll need to look more into it, and consider turning my fuel pressure from 58 - 53 or 55 psi. It's a good start to get these new 96lb low impedance injectors tuned in. I'll be looking into E-93 and other race fuel around PDX next. Also after I've analyzed the tune and checked it all I'm going to turn up the boost.

Datalog 140828 MegaSquirt.JPG

My injector dead time is 1.1- 1.2/didn't run on .5 - .8 like some people talk about.

[nathaninwa]

PDX? English Racing out in Camas has E98 on tap

[nathanhardy]

this info really helped me with my tune.. id run the fp at the injector test pressure otherwise it ups the hr rate

Ok, let's back up to the basics. You need to calculate your injector flow rate for this setup based on your horsepower level, number of injectors, and BSFC. This page explains it well http://www.megamanual.com/v22manual/minj.htm#size The equation is:

InjectorSize = (HorsePower * BSFC) / (#Injectors * DutyCycle)

Assuming you want to make 400 HP, have a BSFC of .6, 6 injectors and a max duty cycle of .90, then you'd need 44 lbs/hour out of each injector.

How much flow rate are you getting out of your 42 lb injectors at 4.5 bar? I'm assuming when you say 42 lb, you mean that's their flow rate tested at 43.5psi (3 bar). When you put 4.5 bar behind them, you're getting 49 lbs/hour out of them. Use the calculator later on that same page to convert to different pressure and flow rates. So you have way more fuel than you need for 400 hp and the other assumptions above. Or to put it another way, using the same InjectorSize equation above, using 49.3 lbs/hour and solving for duty cycle, I get 81%. Also, at this fuel pressure, I get a req_fuel of 6.0 not 7.1.

So I would set the fuel pressure closer to 3 bar, which would give you a theoretical duty cycle of 95% assuming 400hp and BSFC of .6. I agree that 95% is a bit high, but I'd make pulls with low boost pressure and log duty cycle. If it's lower than 90, I'd raise the boost and make another and check duty cycle again. If I'm under my boost/hp goal and duty cycle is getting high, I'd raise fuel pressure and re-calculate req_fuel accordingly. The idea is to use the smallest injector / lowest pressure you can while still having enough to fuel the engine under load. This will maximize PW at idle. The alternative is to go to staged injection.

As far as the misfire, if you're blowing out the spark, there's no reason for MS to read 150-0 RPM from the crank sensor (and trigger sync losses). In fact, I was blowing out spark on oily plugs at 15 psi and the RPM read correctly. The engine coming to a stop from one data point to the next (and then back up) is also impossible. I also noticed that when you had the misfire, the throttle plate went way down and back up. You need a stiffer spring there.

[kaeman]

Ok my 2 cents worth.
If the injectors are rated for 96lbs/hr @43.5 psi then run them there. Set your fuel pressure to 43.5 psi.
Also since you have a ms3 there is no reason that you don't know the real deadtime of your injectors. Do the required testing in the test mode with the correct fuel pressure.
Don't guess or use someone elses info, make sure your info is correct by using the setup that will be running the injectors.
If you are putting in a corrected dead time, then maybe the fuel pressure increase above what the injectors were designed at could make them slow to open and quick to close, and possibly unreliable.
Don't adjust the settings until it runs, find out the real info.
PUT the correct info in then see what happens.. before making changes.
DOing the little extra work on your part may save you a blown engine or other broken parts later on.
GOOD LUCK.

[nathanhardy]

X2 ^^^^