Question About Engine Tuning

[androbud]

Alright, trust me this is not something I'm just going to jump into, but I was curious so here goes.

What would I need to do an engine tune to my 96 GTS? I have the car and a laptop. From what I understand I need the following:

- a laptop or handheld device to run datalogging software
- datalogging software for reading and logging engine parameters
- a VEC1/VEC2/AEM to actually make to adjustments
- A/F sensor

Is it possible to use an OBDII scanner with a software program to actually make adjustments or is it ABSOLUTELY necessary to use a VEC type piece of equipment? From what I understand a VEC unit is like a more advanced hypertech tuner or no?

Can I use a VEC to tune other cars as well? I would like to maybe start tuning on a less expensive engine but I would rather not waste money on two different sets of tuning tools.

At what HP range would I need a wideband O2 sensor? (They're pretty expensive)

I have a friend who tuned his integra using only a laptop with some tuning program and a chip burner. Is a VEC like a "chip burner" that uses "cards" instead of "chips"?

I've searched the forums and I can't seem to find a clear cut answer to my questions. Feel free to correct any mistakes.

 

[KenH]

Your list looks pretty good to me. I went through the process you are considering about 2 years ago, so I'll give you my 2 cents worth.

Most cars like Chevy's can be tuned just using software on a laptop that can reprogram the stock PCM to do what you want it to do. Dodge doesn't let you do something as simple as that, so that is where a device like the VEC2 comes in. It is a programmable piggyback unit that allows you to primarily control the timing and air/fuel mixture during WOT while leaving the PCM programming stock. The VEC2 can be programmed using cards, or you can connect directly to it with your laptop and tune as you drive which is what most people do. The cards are mainly useful for saving and changing between a couple of programs without having to hook up a laptop.

The AEM unit on the other hand replaces the entire PCM and provides greater control, but you have to program for more operating conditions, like idle. I don't think that it is a beginners type of system, but the VEC2 can be.

If you connect to the ODBII stream with your laptop, you can monitor some engine parameters, but you cannot change any of the tuning parameters like timing or A/F. You can monitor the stock O2 sensors for instance, but that is mostly worthless for tuning since you tune for WOT conditions and the stock O2 sensors aren't even used at WOT and are not accurate for the A/F conditions that you want to tune for at WOT. The ODBII stream can be handy for diagnosing things like TPS sensor problems.

Without a wideband A/F meter, any tuning you would do would be in the dark, no matter what HP level you are at. It is a must have as far as I am concerned if you're going to mess around with tuning. There are no safeguards with the VEC2 and it would be possible to damage your engine if you got things too out of whack. The concern is not as high as it would be with forced induction, but I wouldn't chance it myself. You can also put it on the dyno and tune there, but a couple of sessions will pay for a WBO and they are coming down in price.

As for using the VEC2 on something other than a Viper V10, I doubt that it would work as it is built pretty specific for that application, but I don't know for sure.

 

[androbud]

Ah, I didn't realize the stock O2 sensors weren't used at WOT. Now I see the need for a wideband sensor.

So if the VEC2 is not used to change fuel curves at normal idling speeds then I guess you couldn't do something like lean out the engine at low loads to get increased gas mileage? This is what my buddy did to his integra and he can get around 36 mpg and still make 300whp in his integra. (turbo of course)

I read on here of one guy getting in the upper 20's for gas milage but still made crazy hp with a turbo setup. Is this kind of tuning only possible with an AEM?

 

[KenH]

The VEC2 allows you to change the low speed A/F, but since the stock PCM is in closed loop mode and monitoring A/F with the stock O2 sensors, it will try to add or remove more fuel to try to get it back to where it thinks it should be and so you get a tug-a-war going between the two systems and eventually it will throw a too rich or too lean code. About the only use for the VEC2 at idle is to use it to compensate for when you install larger fuel injectors or to fine tune fuel delivery between the cylinders.

At WOT, the PCM goes into open loop mode which means that it just starts running off some built in tables. If the VEC2 is used to modify operating parameters when the car is in open loop mode, the PCM is blissfully unaware. Since the AEM unit takes over all the PCM functions, it can be tuned for what you are seeking, but again it is not a beginners type of system and the $2800 or so it will cost will buy a lot of fuel.

I think you're going to need to be happy with 20mpg on the highway with 400+hp to the tires.

 

[Schulmann]

So if the VEC2 is not used to change fuel curves at normal idling speeds then I guess you couldn't do something like lean out the engine at low loads to get increased gas mileage? This is what my buddy did to his integra and he can get around 36 mpg and still make 300whp in his integra. (turbo of course)

I read on here of one guy getting in the upper 20's for gas milage but still made crazy hp with a turbo setup. Is this kind of tuning only possible with an AEM?

You can do it easily with the VEC2.
I can get 26mpg out of my 600hp Viper on highway.
The stock oxygen sensors are located at cylinder #5 and #6.
So you left with 8 cylinders to lean out.
But to be on the safe side you really need two WBO sensor.

Usually I try to lean out the cylinder to 15.5 - 16.0 AFR for 85mph (1750rpm).
The drawback is the hesitation between 2000rpm and 3500rpm under vacuum.
Under boost I add a little bit more fuel.
Has been working great on highway.
I beat everybody in my club by a quater tank on highway.

36mpg is a lot even for a Toyota prius.
Are you sure about this number ?

 

[androbud]

Yeah he did really get about 36 mpg.

oops I just remembered that he actually had a gas mileage tuning and then a power tuning where he only got about 25 mpg. I had forgotten he had both. So no he didn't get 300whp on the mileage tuning but it was very easy to switch back and forth.

Another question: Do you need the WBO2 sensors in line at all times or only during the tuning?

Are the WBO2 sensors just a tuning tool or do they replace the function of the stock O2 sensors when a VEC2 is in place? I know they don't go in the same place as stock ones because excessive heat can destroy them apparently.