# 85 cis e poor mileage



## jdstrd (Jul 3, 2008)

I have a 85 gli that was getting a consistent 30 mpg that now gets 25 mpg-

What had had prior-

TT 270 Cam
9* of timing
9.5-11.1 on my a/f mixture
longer resonator (34")

What I had after-

I put in new inj seals TB gasket,cold start inj gasket,cis box gasket,fuel line washers, and control plunger o ring,dpr o rings,fuel dist o ring, all new vacuum lines, 
TT plug wires
TT alum knock sensor
TT 260 cam
Gapped plugs at .32
set timing at 8*
set a/f mixture at 8.4-10.1

28"resonator(other one started to rattle)

I had a 9a rebuilt with new 3rd(1.25) 4th(.93) and 5th(.74) final drive 3.81.1 with a white speedo gear.

I also took it too a buddys shop too check the co2 in the exhaust and it was well in range.

Im not sure what I did, or if its just the speedo gear. But I expected 32 or better. Any thoughts, or input would be greatly appreciated. thanx


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## shortshiftstudios (Jun 4, 2013)

your A/F mixture is rich... the closer to 14.7:1 you are, the better...


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## nbvwfan (Aug 15, 2007)

:thumbup: on the above A/F
N/A idle and cruise you should target 14.7:1
WOT not much more than 12.5:1 with N/A

As for the other changes, the most dramatic I see is similar to what I saw when I dropped a Diesel 5th.
I think your gearing (is great) is too tall for a moderately worked N/A car.
I think you are lugging the engine and have suffered the economy hit due to not being in the peak torque/hp range.

Try running the gears out and/or leaning it out to the above 14.7:1 idle and 12.5 WOT.


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## kwak (Apr 7, 2005)

My 87 GTI 16V has a stock engine with a modified gearbox. It started life as a 16V box and was converted to a 6 speed and I changed the final drive gearing. So now it has 4th(1.13), 5th(0.91), 6th(0.75) and final (3.94). At the end of a 45 minute drive on the freeway at 60 mph the MFA fuel mileage for the trip shows 37 or 38 mpg.

So I would personally rule out gearing of,


> 5th(.74) final drive 3.81.1


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## nbvwfan (Aug 15, 2007)

kwak said:


> My 87 GTI 16V has a stock engine with a modified gearbox. It started life as a 16V box and was converted to a 6 speed and I changed the final drive gearing. So now it has 4th(1.13), 5th(0.91), 6th(0.75) and final (3.94). At the end of a 45 minute drive on the freeway at 60 mph the MFA fuel mileage for the trip shows 37 or 38 mpg.
> 
> So I would personally rule out gearing of,


I indicated the gearing because the drop I saw going to the .74 fifth with my supercharged application may have been partly due to the RPM at speed and the parasitic draw of the G Lader.
Additionally, depending on the style of driving mileage can be dramatically affected. I suggested this based on the aforementioned gearing update the OP gave detail. 
What I found to up my mileage was through some trial and error in shift and throttle position. My mpg prior to my swap was upper 27's to 29. After swap it dropped to 26 to 28, and with some monitoring of my driving style I got back to consistent upper 27-29.
You cannot rule out the gearing, plus you built a 6 speed so it is not exactly the same point to counter gearing not being a factor.

In short though, the biggest MPG hit I see would be with the A/F. OP were you meaning to say you set the DPR current to the above stated A/F values? If so, that lower DPR current may have effected your mileage as the ECU may be running a richer base mixture across the range of the sensor plate travel.

kwak, can you let me know where/how you built a 6 speed from a 5 speed? I would really like to find out for one of my upcoming builds.
Thanks


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## kwak (Apr 7, 2005)

nbvwfan said:


> ...may have been partly due to the RPM at speed and the parasitic draw of the G Lader.


The car in the original post does not have supercharger drag, but does have modified gearing.



nbvwfan said:


> You cannot rule out the gearing, plus you built a 6 speed so it is not exactly the same point to counter gearing not being a factor.


That is why I provided gear ratios being used. If the original posted car has a top gear of .74 with final drive 3.81 and mine is .75 with final drive of 3.94, the gearing is comparable regardless if our gearboxes have 4 gears or 6. Cruising at 2500 RPM in the OP car is 61 MPH. With my gearing 2500 RPM is 58 MPH. The point was to show that with comparable gearing, much more fuel mileage is available than what the OP is getting.



nbvwfan said:


> kwak, can you let me know where/how you built a 6 speed from a 5 speed? I would really like to find out for one of my upcoming builds. Thanks


(off topic from the original post)16V gearing is silly short in top gear. I was always reaching for another gear when there wasn't one. I have an Option6 conversion from VL Enterprises from way back. While I have read many bad things about work Vince has done, the gearbox he built for me has 150,000 miles on it.


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## nbvwfan (Aug 15, 2007)

kwak said:


> The car in the original post does not have supercharger drag, but does have modified gearing.


I know, *my* car is supercharged and CIS-E



kwak said:


> That is why I provided gear ratios being used. If the original posted car has a top gear of .74 with final drive 3.81 and mine is .75 with final drive of 3.94, the gearing is comparable regardless if our gearboxes have 4 gears or 6. Cruising at 2500 RPM in the OP car is 61 MPH. With my gearing 2500 RPM is 58 MPH. The point was to show that with comparable gearing, much more fuel mileage is available than what the OP is getting.


Mine is the same final drive as his with a .76 5th from BrokeVW.com, when I did my conversion in car and drove it I noticed I had to shift my driving style in order to up economy. If you drive WOT or a modified gearset, like an original gearset, you will have a drop economy. I made the point as such, and did not need someone countering this as inaccurate information. My economy *did not go up* as I had hoped, and that was due to the parasitic drag of the G Lader. This, coupled with a noticeable drop in RPM outside the peak HP/Torque, one would see a drop in economy as the engine is not at peak efficiency. But the 8Db noise reduction was the other thing I was after and I am happy with the 5th overall, especially Dailying mine with the occasional 10 PSI burst.



kwak said:


> (off topic from the original post)16V gearing is silly short in top gear. I was always reaching for another gear when there wasn't one. I have an Option6 conversion from VL Enterprises from way back. While I have read many bad things about work Vince has done, the gearbox he built for me has 150,000 miles on it.


I asked because you told, thanks for the information, silly short is what VWOA decided we in america would like in spite of the economic MPG hit a high revving 16V runs at highway speed.


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## kwak (Apr 7, 2005)

nbvwfan said:


> If you drive WOT or a modified gearset, like an original gearset, you will have a drop economy. I made the point as such, and did not need someone countering this as inaccurate information.


I drive a modified gearset (very similar to the original poster) and have an increase in fuel economy. I provide this information in an attempt to help the original poster sort through his question. Apologies if this contradicts your information.

Also, apologies to the original poster that we hijacked your thread.


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## nbvwfan (Aug 15, 2007)

kwak said:


> I drive a modified gearset (very similar to the original poster) and have an increase in fuel economy. I provide this information in an attempt to help the original poster sort through his question. Apologies if this contradicts your information.
> 
> Also, apologies to the original poster that we hijacked your thread.


My apologies for taking it personally.
The OP still has not replied so the ongoing spontaneous debate might just be thread filler.

I was surprised my MPG did not go up with my 5th conversion, I guess I had unrealistic ideas of a surplus of power with outrageous economy.


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## jdstrd (Jul 3, 2008)

thanx for the replies. Im going to have to take to a shop to have it tuned with a wide band.


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## nbvwfan (Aug 15, 2007)

jdstrd said:


> thanx for the replies. Im going to have to take to a shop to have it tuned with a wide band.


I missed this in the original post.
QUOTE=jdstrd;84266310]and control plunger o rings [/QUOTE]

My bet is you have the Control plunger stop depth slightly out of spec.
This can be set pretty easily.
From memory on 1.8 CIS-E

Top of meter to pivot bearing should be 19mm +.5mm/-0mm That is the sensor rest position
This same measurement needs to be from the bottom of your fuel distributor to the tip of the control plunger 19mm +0mm/-.5mm.
If it extends further then your entire fuel curve is offset.
From what you describe it sounds like you may have screwed the control plunger stop position a bit too low and your mixture is off by that margin.

CIS has multiple "zero's" Idle mixture, DPR base setting, Sensor rest position, and Plunger stop depth. All effect eachother.

Adjusting the mixture screw hooked to a Wideband can make up this, though it effects other things like idle and WOT A/F.
Just thought I would give some other tips on what I am a bit more adept at helping on.


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