Tuning - where to start?
04-07-2011, 11:22 PM
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Launching!
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Tuning - where to start? downloaded tuner cats and ordered a cable. also got a obd1 pcm to use once i do my cam swap. so the question is, how do i know where to start with the tune? by this i mean is there certain things that should be changed right away and progress by datalogging? or throw the cam in and start right from the stock tune? is it going to hurt anything to run an aftermarket cam until i can develop the tune? i'm pretty sure im going to use the hotcam i have but its got some flaws so i'll have to get someone that knows something to take a look at it and see if its useable or if i might as well go with a cc503 or something of that caliber. obviously i'm just starting with this and taking if step by step so please try to keep the lingo simple as possible. BTW the car is a daily driver and current mods are in my sig. does anyone have a .bin file that will be a good baseline for me?
04-08-2011, 02:11 AM
#2
I like to start tuning idle. Give the cam the timing it wants at idle. Dial in the MAF tables to get a BLM reading close to 128. Then start working on the off idle transition, and low speed driveability.
Again, get the BLMs close to 128 and watch for any signs of transitional spark knock, or dead spots in the throttle. If it's idling, transitioning, and cruising low speed nicely, then start doing some 1/2 to 3/4 throttle pulls and watch the 02s (or wideband preferably), spark advance, and knock retard.
When you've got that polished, the do some WOT pulls and figure out what AFR and Timing the engine wants by reading the plugs. You need to install some new plugs, do a solid WOT pull through the gears really loading the engine then immediately shut down and coast (safely....) to a stop. Pull the plugs (at least a couple from each bank) and read them.
The last thing I usually do is go back and work on medium to brisk speed cruising as that's where the car will spend most of its time. 30-45 MPH in town, and 55-70 MPH on the highways. I do this last because if you really want the tune be right, this is the driveablity part of the tune that will usually take the most time. Not always, just depends on how pick you are I suppose.
This isn't all I do. I like to get a feel for the powerband of the engine, and shape the spark advance curve accordingly. If it's a stalled auto car you can get a little more aggressive under the stall without worry of knock, then taper it off where the stall starts to "catch". This will make the car flash the stall much harder, and make it more fun to drive on the street and hit the tires harder on the track. Of course there's always too much of a "good" thing, and you could have traction issues, so this area of the tune can be useful to get familiar with to really dial the car in to be consistent and leaving out of the hole to the limits of the suspension and tire combo.
You also need to eventually get it on a dyno, and look at the power curve, both shape and duration. That way you can tune the shift points and finalize the spark curve. Beware though that things DO change when you get the car back on the street, as the dynamic loads on the engine can be much different than a smooth pull on the dyno. That's why I feel the ultimate is a street tune first, then dyno for max power / shift points, shape of the curve, then back on the street to final tweak the dyno tune you just did.
If it's a 1/4 mile car you spend a lot of time tuning it at the track as well.
The trans tuning on an auto car is very important as well for driveablity AND for performance, and is really a whole nother subject in itself.
Don't really know how in-depth you're wanting to get with the tune. If you simply want it to run decent with the cam you can get there pretty easy. If you want an OEM quality tune that really maximizes the potential of the engine. It takes time, and knowledge, trial and error, patience, perseverance and experience.
My best suggestion would be that if you're unfamiliar with tuning, first off read all you can about tuning from credible sources, get very familiar with how OBD II logic works, GM platform in particular. Then purchase a mail-order tune from a reputable tuner, and start comparing it to a stock tune and figure out why the changes were made, and how they affect the car.
I would only use Ed Wright, Moe Bailey, or Ion Soltan for mail-order tunes.
.02, hope it helps.
Again, get the BLMs close to 128 and watch for any signs of transitional spark knock, or dead spots in the throttle. If it's idling, transitioning, and cruising low speed nicely, then start doing some 1/2 to 3/4 throttle pulls and watch the 02s (or wideband preferably), spark advance, and knock retard.
When you've got that polished, the do some WOT pulls and figure out what AFR and Timing the engine wants by reading the plugs. You need to install some new plugs, do a solid WOT pull through the gears really loading the engine then immediately shut down and coast (safely....) to a stop. Pull the plugs (at least a couple from each bank) and read them.
The last thing I usually do is go back and work on medium to brisk speed cruising as that's where the car will spend most of its time. 30-45 MPH in town, and 55-70 MPH on the highways. I do this last because if you really want the tune be right, this is the driveablity part of the tune that will usually take the most time. Not always, just depends on how pick you are I suppose.
This isn't all I do. I like to get a feel for the powerband of the engine, and shape the spark advance curve accordingly. If it's a stalled auto car you can get a little more aggressive under the stall without worry of knock, then taper it off where the stall starts to "catch". This will make the car flash the stall much harder, and make it more fun to drive on the street and hit the tires harder on the track. Of course there's always too much of a "good" thing, and you could have traction issues, so this area of the tune can be useful to get familiar with to really dial the car in to be consistent and leaving out of the hole to the limits of the suspension and tire combo.
You also need to eventually get it on a dyno, and look at the power curve, both shape and duration. That way you can tune the shift points and finalize the spark curve. Beware though that things DO change when you get the car back on the street, as the dynamic loads on the engine can be much different than a smooth pull on the dyno. That's why I feel the ultimate is a street tune first, then dyno for max power / shift points, shape of the curve, then back on the street to final tweak the dyno tune you just did.
If it's a 1/4 mile car you spend a lot of time tuning it at the track as well.
The trans tuning on an auto car is very important as well for driveablity AND for performance, and is really a whole nother subject in itself.
Don't really know how in-depth you're wanting to get with the tune. If you simply want it to run decent with the cam you can get there pretty easy. If you want an OEM quality tune that really maximizes the potential of the engine. It takes time, and knowledge, trial and error, patience, perseverance and experience.
My best suggestion would be that if you're unfamiliar with tuning, first off read all you can about tuning from credible sources, get very familiar with how OBD II logic works, GM platform in particular. Then purchase a mail-order tune from a reputable tuner, and start comparing it to a stock tune and figure out why the changes were made, and how they affect the car.
I would only use Ed Wright, Moe Bailey, or Ion Soltan for mail-order tunes.
.02, hope it helps.
04-08-2011, 02:16 AM
#3
One other thing I forgot to mention is you'll also want to work on eliminating false knock. Provided you're installing roller rockers and/or headers with the new cam.
The easiest for most of us is to purchase an LT4 knock module, and play with the Fast Attack Recovery Rate, and being conservative with the timing so as not to induce knock.
1/2 a degree of too much timing can induce knock and make the PCM pull several degrees. It often takes only a small change at the area which knock occurs to prevent it. The PCM is also set to aggressively remove timing due to knock, and gently feed the timing back in, for obvious reasons. This can be tuned as well.
Ed Wright can further desensitize the knock detection in the tune, so that the LT4 Knock Module is not needed. I dont know which other tuners can do this if any. I can't because I haven't taken the time to build the parameters into my tuning software, and I probably wont because I'm switching to LSx ignition.
The easiest for most of us is to purchase an LT4 knock module, and play with the Fast Attack Recovery Rate, and being conservative with the timing so as not to induce knock.
1/2 a degree of too much timing can induce knock and make the PCM pull several degrees. It often takes only a small change at the area which knock occurs to prevent it. The PCM is also set to aggressively remove timing due to knock, and gently feed the timing back in, for obvious reasons. This can be tuned as well.
Ed Wright can further desensitize the knock detection in the tune, so that the LT4 Knock Module is not needed. I dont know which other tuners can do this if any. I can't because I haven't taken the time to build the parameters into my tuning software, and I probably wont because I'm switching to LSx ignition.
Last edited by gregrob; 04-08-2011 at 02:29 AM.
04-08-2011, 11:18 PM
#4
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Thanks for the reply Greg. For now I don't plan on getting THAT far into it. like I said, its a daily driver so it needs to run reliably first and then I'll start tweaking things. I'll be doing the cam swap at the end of july when I take vacation and would like to have as much ready as possible. I'll get the rest of the parts together and contact Ed as he seems to be very reputable. I suppose spending a little more money now will be better than fixing my uneducated screw ups right away and give me a place to start. thanks again for the guidlines. Anyone have a hotcam or something similar incase i find out mine is garbage?
