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Comptech SC Results? Help/info appreciated

Joined
5 June 2002
Messages
307
Location
San Diego, Ca
Took the car to get some dyno A/F, hp, torque, fuel pressure information today. I would appreciate any learned input on my findings. I have a '95, with headers, and exhaust.......HID's too.':D'

To start, at idle, the rail pressure was sitting at 40 psi (with 20 inches? of vacuum), but 50 psi with the vacuum line removed (static pressure). Was getting 355 hp/265tq, but with a hint of pinging, and 12.5 to 14.0 A/F. I gradually raised the rail pressure via the FPR at 2 psi intervals. Finally boosted the rail pressure up to 49 psi (60 psi with the vacuum line removed) and the pinging was gone. Rail pressure went up to 95-100 psi at 8K rpm's. The A/F ranged from 11.9 to 12.6. The FPR adjustment screw was about 0.2 inches above the lock nut, close to all the way in. I was getting 359.8hp/272.0tq.

After this run we let the car set for 30 minutes for lunch, and I reset the ECU (pulled the 7.5 amp fuse for 45 seconds). Started the car after lunch, and let the car idle for 4 minutes, and ran three runs.


A/F HP Torque

Run #1 13.1 - 11.0 358 260
Run #2 12.2 - 10.8 358 264
Run #3 12.6 - 11.9 360 272

NOTE: Run #3 hp/tq curve was virtually linear, unlike run 1 & 2 which had the usual V-TEC blip at 5300 rpm's.
NOTE: According to Comptech, the FPR under vacuum should be 40-44 psi, and 58-62 psi static pressure.

Questions:

Is the FPR adjustment screw too far in compared to others?
What A/F ratio should I be looking for?
As runs 1,2,3 seem to be converging on the right/desired a/f, and have the most hp & tq, does the ECU have a learn mode?
What rail pressures are others getting/using?


Any comments/questions would be greatly appreciated.

Thanks,
Gene:D :D
 
I'll offer just a few thoughts but I can't give you most of the requested specifics.

My primary concern is the A/F up around 12.5. Where in the curve was that? If it is early before much boost is developed then you are OK, but if it rises from 11.x to 12.x as RPM and boost increase then there is reason for concern. 12.5:1 is great for a normally aspirated engine but with the SC it is probably too lean while on boost. If anything you should be starting at that value around atmospheric then decreasing (getting richer) as boost increases with the mixture at perhaps 11.x:1 at redline. Exactly where depends on things like how much boost you get, how much timing is being pulled, etc. Just because you stopped hearing the ping doesn't mean it was completely gone so you may want to dial in a bit more after you think it stops.

The blip at 5300 is too low for VTEC and is probably the variable intake device in the manifold (sorry, I'm brain-dead here and can't think of the real name).

We believe that the ECU does "learn" over time and trim settings accordingly. In your case it probably didn't alter fuels much since your runs are "open loop" and it only reads the O2 sensors in low load closed loop mode and therefore had very little time to learn. But since you had pinging in the prior runs it may have trimmed back from them and then removed the trim from the timing map. Actually, those sensors may also impact fuel although I would think the emphasis for ping would be timing given emissions controls.
 
I can scan and email them to somebody, but I have tried in the past to post with no success. If anyone can post picts, let me know I will email you the scan, or call 760-931-9100

Thanks,
Gene
 
What size injectors are you running with the S/C? with rail pressure at....
(Rail pressure went up to 95-100 psi at 8K rpm's) I am also wondering what your BSFC is.
Has anyone indicated it to you? after you indicate injector size I have a few questions about fuel delivery and your S/C if you dont mind,it would be a great help to get your feedback.

I am receiving many requests to add nitrous on top of cars running the Comptech and want to do my homework on feasibility . I dont like the idea overall of putting nitrous on this setup without knowing how Comptech has setup fuel management or on cars without built internals.

Several people say they are willing to risk it even though I advise not to do it, although I have changed a few minds.I just cannot justify doing it to make a buck with possible risk to the motor (I just want to hear some specifics as I do not know them) TIA!
 
I'm not quite sure was "BSFC" stands for, please elaborate. However, I'm running stock injectors, and it is the standard 6 psi system. The guys at the dyno said the next step is to add a 15-20 shot nitro shot to the system. It will help cool the intake temp, and assist with the poor 91 octane gas we have here in San Diego. Call me 760-931-9100 to discuss further.
 
emvanderpol said:
I'm not quite sure was "BSFC" stands for, please elaborate. However, I'm running stock injectors, and it is the standard 6 psi system. The guys at the dyno said the next step is to add a 15-20 shot nitro shot to the system. It will help cool the intake temp, and assist with the poor 91 octane gas we have here in San Diego. Call me 760-931-9100 to discuss further.

Gene, don't put nitrous on your car. it will hurt not help your low octane and increase the need for higher octane and timing retard. I will call you for sure this week. running at 100 psi on the stock injectors at 8000 RPM makes me a little nervous. it is IMHO time to step up to larger injectors and turn down the pressure. I am very opinionated about fuel delivery and injector sizing for a given application. others may feel your system falls within reasonable specs on fuel pressure and injector size and duty.
 
Pinging / Timing

Just because you stopped hearing the ping doesn't mean it was completely gone so you may want to dial in a bit more after you think it stops.

Excellent statement, which begs a perhaps difficult question to answer. When tuning for A-F ratio and timing, we use a wide-band oxygen sensor to tell us when the injector pulse is set properly. (Mine is 11.9:1 under boost.) However, what feedback parameter do we use for timing?

As I understand it, timing advance is added to increase HP up to the threshold of when pinging is heard. At that point, dial out timing until the pinging is no longer heard. One could argue that while done on a dyno, this is the "optimum" timing setting for a that particular engine. But if pinging can go on undetected because it is a silent killer, how do we determine what the real total timing should be? Plug in a Honda data scanner? BTW, this is a tool that costs the dealerships over two grand, so it is not like this option is available to everyone. Even if it was, what quantitative timing value do we look for to ensure the pinging silent killer is gone?
 
sjs said:
...The blip at 5300 is too low for VTEC and is probably the variable intake device in the manifold (sorry, I'm brain-dead here and can't think of the real name)....

I was discreetly reminded that this cannot be the case since the VVIS is removed as part of the CTSC design. Well, I said I was brain-dead. So what causes that blip on a CTSC car? This has probably been discussed before but might be resonance’s in the intake tract? Or does it even exist on them at all? (Only semi-conscious tonight)
 
Re: Pinging / Timing

AndyVecsey said:
... When tuning for A-F ratio and timing, we use a wide-band oxygen sensor to tell us when the injector pulse is set properly. (Mine is 11.9:1 under boost.) However, what feedback parameter do we use for timing?

What you monitor is knock sensors, either stock or add-ons. That's another advantage of a standalone ECU since they monitor and log the sensors as well as the timing retard induced by them. In theory they will detect what we can't hear. Tuning then becomes a balancing act between air/fuel and timing to achieve the most power without undue risk.
 
Knock Sensors

What you monitor is knock sensors, either stock or add-ons.

Who is a manufacturer of aftermarket knock sensors?
 
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