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High VE numbers

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Hi guys, I just started tuning my haltech elite 2000 and am getting higher than I would expect VE numbers. I’m in the 80s and 90s at idle. I’m using Injector Dynamics 725 injectors and have entered all of the data from ID, It idles nicely just has high numbers. I bought ID injectors to avoid any problems with dead times etc but I can only assume that their data is off somewhere. Any ideas how to check and see where I’m off or should I just ignore it and give the ecu the numbers it needs? The engine is a Toyota 1fz-fe.

I appreciate any help or advice anyone can give.

Are you sure differential fuel pressure is actually at spec? That is probably the most likely cause unless you have a very radical cam, then overlap/ injector phasing may have some influence/allow unburned fuel the pass through the engine.

Is this a return fuel system or a returnless fuel system? Have you confirmed fuel pressure?

Hi Raymond, I’m a member of your RX7 tuning group also :). It’s a return system. With the vac reference disconnected it’s set at 43.5 psi. The fuel pressure is lower at idle with the vac hose connected. I can get the exact pressure at idle this evening when I get home.

edit:pressure at idle is 33psi with vac connected.

The cams are stock. Most of the engine is, I have forged internals but otherwise nothing has really changed.

Thanks for the reply’s.

Ah, good to see a fellow traveler :) Can you post screenshots of your injector related settings (deadtime table, injector size, etc)? Another thing to keep in mind is that air temperature and fuel temperature can impact it. What ambient temperature is it? You probably don't have fuel temps but what are your air temps, and can you post your air temp compensation table(s)?

http://injectordynamics.com/injectors/id725/ you can see the nominal flow rate is at 3.0 bar and 52C fuel temperature.

The temps here are usually 80s -90s. I haven't done anything with the air comp tables yet but have attached a screen shot of the default table for my setup.

Attached Files

So you're saying that the ambient air temperatures are in the 80s-90s Fahrenheit ? What are your intake air temperatures (Celcius is fine) ? So standard SAE J1349 condition is about 77F or 25C in front of the air filter (dirty air duct that leads into the airbox, or in the cone filter if you don't have a box). That standard condition is meant for climate controlled labs though. But then you have to consider manifold temperatures and heat soak. Where is the IAT sensor located?

This could be a case of the IAT sensor getting hot. It's normal to be in the 35-55C range under the hood, if not higher considering your ambient is over 30C. So as that temperature is climbing it will start pulling fuel out, following the IAt correction table. Then if you are running open loop fueling you will keep adding to the VE table to bring the fuel back in line. The other thing to keep in mind is that these tables are based on laws of physics but the exact numbers can end up being arbitrary, in the sense that in the end you put in whatever numbers you need to make it work.

So you have a few options here, assuming it's just temperature effects at work. You can set the VE table as you have it now. You can shift the VE table lower in that area and adjust the IAT compensation tables based on sensor readings and sensor location. So for example, make the "0" area of the map at higher temperatures. You could adjust the injector flow rate or related settings but I wouldn't do that at this point. Or just turn on closed loop fuel and if you're within 5 to 10% correction during idle and cruising call it good.

IAT is in the pipe about 10” before the throttle body. It doesn’t really get heat soaked and the temps are not usually more than 10 degrees F above ambient. Turned on closed loop and it’s around 3% correction. I just didn’t want to tune the whole map only to find out the VE table was way off and I have to mess with the dead times or flow. I’ll put in some hours this weekend and see where it gets me. I appreciate the advice.

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