# DPR tuning



## johnnyGO (Feb 23, 2009)

Im about to give it a go for the first time but I wanted to ask the guys that have done it how much of a peformance change did you notice? Alot, a little?


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## wclark (Mar 28, 2001)

*Re: DPR tuning (johnnyGO)*

If you are referring to the couple online articles on turning down the DPR current a couple millamps from stock for performance, I think its mostly placebo. It will richen the WOT a little which in the right direction but it falls way short of producing AFR's like 12.5:1 to 13:1 where the most power is produced. 
About 5 years ago, on the dyno I had to run the CO screw down to the equivalent of about -20ma at idle to get my race 8V to 13:1 and never did see 12:5 where it later was found to produce max power. Of course CIS-E wont go below zero ma so the cars idle and lower RPM part throttle was like poop because it was way too rich. It didnt say there of course because I could only drive it at WOT, and it was then I started working on enrichment modules.


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## rcortez13 (Nov 21, 2005)

*Re: DPR tuning (johnnyGO)*

If your talking about removing the DPR and adjusting the 2mm hex screw hidden under the flathead screw then yes it's helps. If you have a bigger cam(s) then it's necessary. 
With the help of my wide band I adjusted my DPR and I'm getting 13-13.5/1 AFR at WOT. My initial adjustments yielded around 12/1 AFR at WOT. The capability to get more fuel is there!


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## ziddey (Apr 16, 2006)

*Re: DPR tuning (rcortez13)*

Doesn't cis-e indeed have the ability to go negative, at least with cars that utilize an idle switch. Doesn't it goto -50ma or something for deceleration fuel cutoff?
And about taking off the dpr to adjust it, doesn't that again only produce a shortterm "instantaneous" response? So for cars that use cis-e but don't have a wot switch, wouldn't the ecu quickly "recover" based on o2s response?
After I get my car smogged, I'll definitely be playing with the dpr winding, along with a cam hopefully. But just curious.

As for changing the centering of the dpr, be careful not to go too far, since it'd change your cold running condition, before the o2 is able to give feedback, and the car is running off the cts. I guess if anything, it'd just mean you'd have a "faster" car before the o2 kicks in to bring things back to normal


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## WaterWheels (Aug 14, 2005)

*Re: DPR tuning (ziddey)*

Yes, CIS-e and Motronic can both go negative. For over-run situations (down hill coasting and the like) as you suggest and also as the engine speed limiter.
The DPR is not removed, only the mixture screw is adjusted while watching the mA reading on a multi-meter. The way it works is simple really. CIS-e is just an electronically "trimed" version of basic CIS. Any changes to the mixture screw (piston height) is applied to all engine speeds. Therefore raising the piston height at idle will also cause it to be higher at high engine speeds. At idle the system trims back on the fuel to lean things back out, hense the *LOWER* reading at idle for a richer mixture. At WOT speeds the electronics adds a few mA which richens the mixture even more then the mechanical mixture setting plus causes it to go open loop from the O2 sensor. During normal driving the O2 sensors feedback is used to keep the mixture in line as normal. 
Does it help any to "tune" using the mA reading at the DPR? Yes it does. Is it the kind of tuning that might be needed or used in racing? Depends on the class and just how much of an increase in mixture might be required. For most street users with stock to mild engines, it does help and just the sound you will hear of the engine indicates there is a difference. On an 8v you most likely not hear the difference, but on a 16v the engine quiets down at high engine speeds. Also, yes, cold starting and warm-up is also effected but most times not all that much and is easy to live with.


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## ziddey (Apr 16, 2006)

*Re: DPR tuning (WaterWheels)*

I was referring to http://forums.vwvortex.com/zerothread?id=3070507
"Power Tuning"


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## Longitudinal (Nov 13, 2004)

*Re: DPR tuning (WaterWheels)*


_Quote, originally posted by *WaterWheels* »_The DPR is not removed, only the mixture screw is adjusted while watching the mA reading on a multi-meter.


_Quote, originally posted by *ziddey* »_I was referring to http://forums.vwvortex.com/zerothread?id=3070507
"Power Tuning"

Ziddey is correct here, and I think the OP refers to the same. 
I have done it many times to many cars, and YES, DPR tuning helps. The more modified your engine, the more it helps. Even a stock engine will experience a small improvement, particularly in throttle response and start-up. The DPR is removed for this tuning procedure.


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## ziddey (Apr 16, 2006)

*Re: DPR tuning (Longitudinal)*

so "throttle response" only means until it gets feedback from the o2 and is able to correct? Or would it be drawing more and more air and keep pushing before it can compensate from the o2?


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