tuning question

specops_SC

Registered User
after what kind of mods is it recommended to get a chip or dyno tune? i dont want to do it too early and have to do it again. any suggestions? in my 90 i want to get it to run low 14's on the stock injectors and when i get the 5spd i want to get it into the low 13's. i would get a eec programer but i know absolutely nothing about tuning and dont wanna start screwing things up. thanks.
 
Any SC can benefit from a chip. Initially it will result in anywhere from 5-20rwhp depending on your car's current condition and original factory tune.

As long as you have the stock injectors, airbox, and MAF meter, there is no real *need* for a tune. You have to understand that there is "tuning" which improves the factory calibration, and then there is "tuning" to correct modifications to the factory tune (caused by bolt-on mods done to the car)that have been detrimental to the tune.

My suggestion is that you plan a series of mods that are within your reasonable budget, then get the car dyno'd. After you have completed your mods and have a dyno sheet in hand with AF readout, then I can build you a chip that will correct any possible problems as well as maximize the factory calibration. In this case you will generally make more HP but more importantly you will be able to drive the car with assurance that it is running correctly.

Once you change your MAF, injectors, or airbox, you no longer have any assurance that your car is even running safe, much less optimized. I've seen cars with as little as a pulley, MAF, and CAI that threw the tune so far off that AF went to 16:1 on WOT. This condition WILL blow headgaskets and can result in detonation that can bend connecting rods, melt pistons, etc.

Not trying to scare anyone, but those are the realities of modifying these cars. One thing you don't want to do is get a chip done and then add a new MAF, FMIC, or MPII supercharger etc. That would be a bad idea.

I offer reburns to original purchasers for a very reasonable amount so I wouldn't worry so much about needing a reburn. The most expensive part would be the dyno time.
 
XR7 Dave said:
have a dyno sheet in hand with AF readout

And to add one critical statement, if you do end up getting a tune done, get the A/F done with a bung BEFORE the cats so it is accurate. I and others on this board have seen dynos report A/F anywhere from .75 to as much as 2 points off of the actual #s!

Paul
 
Your better dyno shops will offer a screw in O2 sensor which they install in place of the factory one vrs. stuffing a sampling tube into the tail pipe. Also note that any exhaust leak in front of the sampling point will make readings invalid.
 
XR7 Dave said:
Your better dyno shops will offer a screw in O2 sensor which they install in place of the factory one vrs. stuffing a sampling tube into the tail pipe. Also note that any exhaust leak in front of the sampling point will make readings invalid.

thanks for the clarification. i was thinking they were going to drill a hole in my pipes. lol. so if they have their own o2 sensor, i assume it'll have the extra wiring to hook up to their comps as well as back to the car. do they only do one side or both sides? and if they only do one, which side would you recommend i get the a/f readings from?
 
Your car will run fine W/O one of it's 02 sensors. They just unplug it.

Ideal would be to have a sensor bung in the common part of your Y-pipe, but barring that either side will do ok.


General rules for dyno sessions:

Before scheduling dyno time:

1) Make sure you have correct fuel pressure and sufficient fuel delivery under load.

2) make sure you have only the proper octane fuel in the tank! Don't use race gas unless you have a specific mixture and plan to use it ALL the time!!!

3) Check spark plugs and wires, replace if marginal.

4) Clean your MAF wires and clean or replace your air filter.

5) Check for vacuum/boost leaks

6) check blower belts and if they are marginal, replace them.

7) do not dyno if you have CEL issues. Fix the problems first.

8) fix any exhaust leaks before the dyno session.

At the dyno:

1) Make sure the car has been fully heated up prior to dyno session, then cool intake, blower and IC before pull is performed.

2) Disconnect battery for 30 sec. to clear adaptive memory.

3) make sure IC has airflow. If you have an IC fan, USE IT.

4) especially if your car has a small (stock) IC, always allow at least 10 minutes between pulls and apply some sort of cooling to the motor between pulls if possible. Typical dyno squirrel cage fans work great when pointed directly at the blower/IC for 3-5 minutes.

5) do not waste time running the motor past peak HP. You will merely be adding extreme heat to the blower and IC.

6) make sure that your printout does not reflect any smoothing and reads in SAE HP. If you are not getting consistent tach readings, ask them to move the tach pickup leads. You are paying a lot of money for their service. Make them do it right or not at all.

7) ask for data acquisition if they have it. Some shops can offer you boost information or MAF voltage. This is very nice and worth the extra bucks if they can offer it.

There may be some other things as well, but those are what comes to mind at the moment.

David
 
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