V1 LeoZug's Montana Street Goblin - '05 Cobalt SS donor

[Leo Zugner]

Great! Thanks for the feedback. Out of curiosity, why does the engine now have tuning issues? Is it because some elements like sensors aren’t there any more, etc?

 

[Traé]

Great! Thanks for the feedback. Out of curiosity, why does the engine now have tuning issues? Is it because some elements like sensors aren’t there any more, etc?

My understanding of it is the much shorter intake tube causes problems and the MAF needs to be calibrated at the new location.

I havnt messed with it too too much.
I calibrated the MAF sensor, volumetric efficiency table, and scaled for larger injectors in HP Tuners.
My car runs a lot better and smooth enough for me to call it good and not get too into the weeds.

There are some pretty detailed tuning threads on this forum discussing what to change and why. Also, Goat Rope Garage on YouTube is where I learned to do everything I did to my Goblin.

 

[Ross]

Even your air filter placement can cause the MAF to not read airflow correctly.
Moving the filter as far away from the MAF before tightening the hose clamp, is important.

 

[Leo Zugner]

Awesome. Thank you.

 

[Leo Zugner]

After lots of searching I found a local tuner guy that may be able to help me get the Gob running smoothly. He can come to me and charges $850 and he says he does the maps for fuel, air, etc. I don't know if this is a good price? But I also don't have much choice as he's the only guy I've found and I REALLLLY don't want to do this myself. He said he will do a tune with it in my garage and then will do a follow up after it's driving for no additional cost. Thoughts?

 

[Rauq]

Not a bad idea to have someone with tuning experience help you get the tune straightened out. I don't know what the tuner market looks like in your neck of the woods but I'd imagine you have fewer choices than I do.

You don't have a wideband O2 sensor, do you? It would be something you had to add during your wiring work. It's needed for any tuner to give you a comprehensive tune for making power. If not, tuners typically use a tailpipe sniffer on a stationary dyno. I'd be impressed but not super surprised if your tuner can set one up suitable for driving as a temporary installation. Might be worth asking about, and if you didn't install one and the tuner isn't set up to run their own temporarily, then I'm not sure you need to be paying full tuning prices.

I will say, if your LSJ is otherwise stock and you're not looking to squeeze every horsey out of it, you shouldn't need much tuning to get your Goblin to run fairly well. Yes, the MAF curve and VE tables might take a little tweaking, but a stock tune shouldn't be that far off, and in my limited experience, not so far off that it'd prevent the car from running at all.

 

[Gtstorey]

$850 is a lot for basically tweaking the MAF for basically a stock setup. Unless I'm missing something, that is about all he should have to change. It might get a little better tweaking the VE and timing but this setup should be able to be tuned in a couple of hours. $850 is what it might cost with a heavily modified setup (adding turbo/SC to na motor or major cam/injector/exhaust change).

 

[Leo Zugner]

That all sounds good. Thanks. I didn't install anything extra as far as i know. He also told me will do the initial tune with it just sitting there, then do a follow up tune once I'm driving it for no extra cost. At this point I'm not looking for a ton of power. This thing will most likely be the fastest thing I've ever driven so extra power might not be needed... for now...

 

[Leo Zugner]

So my tuner guy came today and after a while we made some progress but it’s still sort of surging for a while then it dies. It surges to about 950 rpm down to about 450 for a while and then dies. He worked on it for a while but as of right now doesn’t know how to really dial it in. He thought it might be an idle control valve? I have no idea. He’s gonna research and come back in a few days. Any ideas?

 

[Ross]

Smoke test to check for air leaks in the intake, or exhaust? Just a guess, it could be lots of things, but air leaks will cause the sensors to be inaccurate.

 

[Rttoys]

like Ross said, could be a vac leak. Pinch off the brake booster at the tb to make sure it wasn’t damaged during the build, plus that eliminates everything from the engine forward. Check intake area for leaks, super charger, all vac lines.

where is the MAF? Like some have said, if it’s too close to the tb, it may not be reading correctly.

 

[Leo Zugner]

I’ll check for other leaks. This is how I have the intake set up right now.

 

[ah.b.normal]

Mine is, of course, a base model with different computer, but that era's cars do similar things. When left off of the battery for a while initial start up gives a widely wandering idle usually 1800 to 0. Initial "hunting" for low idle was very common in all older computer cars. Mine generally takes three dies to find a useable low and maybe three more do find "a keeper".(and that is just my observation)
A single vac leak will trip the computer up and one malfunctioning sensor hopefully will set a code to give you a clue. Try with the MAF sensor disconnected, it will stumble a lot but the computer defaults to operate around that particular sensor loss.
None of this sounds unusual to this forum. I know this bunch will track this down and you'll move on. They seem to take every problem as a bit of a personal quest. My theory is that we find every trouble request a chance to learn more about these systems for our own car future.

 

[Leo Zugner]

Ok good to know. Thank you. The tuner will come back tomorrow so maybe I will have some progress by then. Also for what it's worth, we tried for almost 2 hours to get it going so I think it's more than the computer searching for a good speed. The tuner kept adjusting the air mix, then the fuel mix, then the idle speed, then the air, etc. For a long time, it would run for about three seconds, then pretty much die, then do one more desperate rev/burp, then fully die.

Does my intake setup seem ok? I've seen a few people mention the distance between the MAF and the throttle body. I'm using the stuff DF sent so I'm not sure how else I could arrange them.

 

[Rauq]

No idle control valve with the DBW throttle body...

Any chance your MAF is in backwards? There should be some arrows to indicate direction of airflow.

The intake setup looks ok to me, only potential opportunity for improvement is to try to match the radius on the intake of the air filter to the pipe to smooth airflow. Filter might need to move up or down that pipe a little, I can't tell from the pic. Let me know if that's not a clear suggestion.

 

[comegetjoe]

No idle control valve with the DBW throttle body...

Any chance your MAF is in backwards? There should be some arrows to indicate direction of airflow.

I can see the arrow in the picture. This is the case.
The arrow should be facing air flow entering the engine.

 

[Rttoys]

the intake is basically the same as mine, so it’ll be fine. You need to look for a drivability problem, not so much a tuning problem. You can’t tune it until it’s running correctly.

 

[comegetjoe]

 

[Rttoys]

Your zoom is better than mine. Good catch. The arrow strikes again.

 

[Leo Zugner]

Oh man! My MAF is backwards?