2003 S2000
Inline Pro 3mm head gasket
Precision turbo (similar to Garrett GT35-R)
GM Boost Solenoid
Log manifold
KManager 3.2.2.0 (Hondata Kpro III)


I am trying to figure out the duty cycle so I can boost-by-gear. My understanding is that the GM boost solenoid is normally open so I input a fixed duty cycle of 20%. I enabled quick spool with the desired boost settings I want and from my understanding, once the target boost is reached the boost solenoid will default back to the duty cycle.

The boost is going over the desired amount, up to 20 psi and I'm not sure why. I was rowing through the lower gears on the street. The boost in 1-2 gears feels sluggish. It's hard to input the boost by rpm based on the duty cycle data logs when it is totally inconsistent!

It's frustrating when it feels more sluggish than N/A in 1-2 gears (and low rpm's) then finally awakens in 3-6.

I want 8, 8, 15, 15, 18, 18 psi boost (for the associated gear 1, 2...n)

I posted a link on the Hondata site with the datalogs and current calibration:
http://www.hondata.com/forum/viewtopic.php?f=14&t=16192

Any advice would be much appreciated!
Thanks!

 

Looks like Hondata is already helping you out some buy my advice would be to turn off the quick spool settings and get the duty lookup tables dialed in first. Turn off the boost controller, see what it makes. Add 10% duty, see what it makes and add that to the table. Add 25% duty, see what it makes. Do that all the way to your target boost. Once you have the lookup table dialed in, you can use the by gear tables to target boost for the RPM/gear ranges you want. It won't be 100% across the board - you will need more duty cycle in the lower gears than in the higher gears for the same amount of boost. Finally, once you get THAT dialed in you should be able to get the quick spool settings dialed in the way you want.

This will take quite a while on the street (and is somewhat dangerous) so if you have the opprotunity, use a dyno.

 

Yeah I posted on both sites to get a broader understanding - I can't upload the logs here for some reason. I was unclear in the process of tuning for the rpm/gear ranges. Initially my thoughts were to input a fixed conservative duty cycle e.g. 20% then put the target values in the quick spool setting. I thought that the GM BCS would regulate those target values in the quick spool settings.

When I was reviewing the datalogs, it seemed odd to see almost no boost 1-2 gears at ~4-5k rpm then accelerate to ~25 psi at ~6.6-8.5 krpm...all with a duty cycle of 20%.

From your explanation, you have to build an empirical table based on the duty cycle in the pressure vs. duty cycle table - without the quick spool option. So would the pressure be evenly spread across the rpm per gear? e.g. 20% duty cycle, quick spool OFF, would I see 5 psi in all RPM range? Or would I see variances in pressure? like 5psi-2k, 7psi-4k, 15psi-8k?

In the meantime, I will follow the suggestions and you are correct...very dangerous doing this on the street.

 

The duty cycle across the gear is dependant on how well your setup is gated. If you have poor wastegate placement (or not enough gate), there's only so much a boost controller can do. But even in the best case scenario a value like a flat 20% will only get you a certain amount of boost in any given gear because each gear puts different loads on the motor which changes the amount of boost made. So to answer your question, 20% might give you your desired boost in first and 2nd gear, but you might need a little more duty cycle to maintain that same boost level in 3rd and 4th (most certainly in 5th and 6th). That's why you tune the duty cycle vs pressure table first, that way the ECU knows how much duty to target for your desired boost in the boost by gear table.

 

Ah, this is very good information - thanks! Hondata suggested switching the ports on the GM BCS - swapping port 2 with the filter port to make it normally closed. Not sure how well it will perform if it isn't designed that way.

Another question, until I get it on a dyno...does fuel follow torque? Last thing I'll be doing is setting vtec. I want to find that smooth transition without bogging down or throwing me sideways.

 

Configuring the BC to be normally closed is safer for the motor because if it fails for any reason, the car will fall back to gate dictated boost level.

I'm not a tuner so I can't comment definitively on your second question. From what I know, torque follows ignition timing.

 

Check it out...quick spool disabled. At 15% duty, I make 22 psi. I have a blue Tial 7 lb spring. I took data at 25 and 45% which showed boost drastically going upwards - I got out of it fast enough though.

So when I make pressure vs duty table...I start out with 15% duty and 20 psi boost? Or should I do redo the table and scale from 1-15% duty cycle?



***Edit*** I found another reference for testing a MAC BCS using the same method:

MAC BCS

While I am investigating the ports on the GM BCS, I would like to verify if I have it wired correctly for the Kpro III. I followed the KManager Help files for reference and used the factory service manual to make the connections.

With no BC enabled in KManager it runs off the spring pressure with no issues - 7 psi (0.5 bar).