GTM Cold Air Intake

[Tony Eupizi]

Does anyone know if the GTM optional Cold Air Intake system will work on the SLC? The GTM has a tee from the throttle body to two tubes forward of the rear wheels? I have the race tail option and if the single tube with the 22 degree downturn has an interference problem I am looking at alternatives.

 

[Bill]

My SLC is setting next to Mike's GTM, which has the optional Cold Air Intake system and the tee. Assuming you place the MAF sensor between the intake manifold and the tee, the tee won't fit under the street tail.

I can't speak for the track tail.

 

[Jack]

It won't fit in a race tail with the above mentioned configuration. The street tail is somewhat
taller.

 

[Tony Eupizi]

Can the MAF sensor be located in one of tubes after the tee? I know the GM manual calls for a minimum of 10 inches from the throttle body with a minimum of 6 inches of straight 4" tubing. The picture in the FFcar option guides shows a small tube (less then 6") from the throttle body to the tee. I was thinking the MAF sensor was in one of the side tubes.

 

[Fran Hall RCR]

It cannot be in one of the tubes, it must be after all the tubes intersect and before the throttle body ,so it measures ALL of the air being ingested by the engine. If it was in one tube the airflow in the other tube would go unmeasured and the engine would not run correctly.

 

[Will Campbell]

I've seen a GTM with a dual intake, with a MAF in one of the tubes. How did it work? One of the tubes was closed off, so you had the appearance of two tubes, even as only one was actually open. IOW, only the tube with the MAF actually flowed any air to the engine.

Perhaps that is the one you saw?

I don't think that one met the standard in the GMPP document, though, as there wasn't a straight of the correct length before or after the sensor.

It would be interesting to know whether or not the owner experienced driveability issues, as that is the likely consequence of turbulent air past the MAF sensor (which the straight lengths minimize).

 

[James]

You could just convert to a MAP (pretty sure it's possible), and then you can have whatever routing you want. You will probably have to do some tweaking with the ECU.

 

[Fran Hall RCR]

James I think you mean speed density

 

[Shane]

Yes, some guys are running the MAF in one tube and blocking the other tube off. And yes, following the GMPP recommendation of placing the MAF in a straight section of 4" tube away from the throttle body and corners makes a huge difference in how well the engine will run. If you try placing the MAF right in front of the throttle body, you should plan on lots and lots of time dyno-tuning, as the MAF will be sending wildly inaccurate info to the ECU, and the ECU will be supplying fuel based on that information.

Save yourself the headache and install a single CAI and place the MAF as recommended.....

 

[James]

James I think you mean speed density

I'm assuming it works one the same principle as a MAP (Manifold Absolute Pressure) IIRC Honda uses MAP sensors on a lot of their applications.

 

[Eric McClellan]

I've always felt that a SD tune was a last resort for a complicated setup.

 

[James]

I looked up some details on a MAP. WOW,, it is quite complicated. You not only need RPM.. but you need Volumetric Efficiency per RPM. The table is quite complex

 

[Preston Brown]

People do it all the time with MegaSquirt and other aftermarket EFI computers... wideband O2 (UEGO) sensors and closed-loop "auto-tuning" can simplify the process of building the VE tables quite a bit.

 

[Michael]

Since the door was opened regarding GTM's, I thought a couple of pictures showing the GTM with the dual cold air intake might help in this discussion.






The mass air flow sensor is placed in the standard configuration.





Mike

 

[Shane]

I guess to expand on Mike's post and clear up my post above, yes, you can do that as long as you have the older style LS1 MAF sensor as shown in his photos. You can also do this with the newer cartridge style MAF, but it is going to be wildly inaccurate and even tiny changes in where you "clock" the MAF in relation to the throttle plate will make major changes in what the MAF is reading. This is why they recommend placing the cartridge style MAF in a straight section on pipe and NOT right next to the throttle plate.

The older LS1 style of MAF is no affected nearly as much since it has a honeycomb insert that serves to straighten and equalize the air moving thru it, so it is less affected by turbulence inside the intake.