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Engine Specific Info and Questions => IDI Engine => Topic started by: overdrivegear on January 17, 2011, 08:52:06 am
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Hypothesis: Giles equipped engines require different gearing to realize increased fuel economy.
I have two 1.6 NA's and here are the specs for each:
87 Cabriolet w/ diesel conversion:
Hydraulic lifter engine
Giles IP
Giles 135 BAR injectors
Stock 1.8 gasoline exhaust with Cat. delete
AGS transmission w/ 0.71 fifth, 3.94 diff (2500 RPM @ 60 mph)
Stock wheels/tires 175 tire width
85 Golf 1.6 NA (2-door)
Solid lifter engine
Stock BOSCH IP
155 BAR injectors w/ Merc nozzles
Stock 1.6 NA exhaust
ACH transmission w/ 0.71 fifth, 3.94 diff (2500 RPM @ 60 mph)
81 Rabbit steel wheels 155 tire width
Other controls in the experiment: both use same weight oil, similar road trip for both cars, similar temperature conditions. Both cars are driven on highway/interstate 55-60 mph, coasting out of gear down long hills, etc.
In the Golf, I never get less than 50 MPG, even driving on mountainous highways. Currently, my record MPG is 56.7 (GPS distance confirmed) but the average is 52.
In the Cabriolet, the best I've been able to do is 46.6 MPG driving 50-60 mph on highway to the Atlantic Coast and borderline hypermiling.
I think I have to go to a transmission with 3.67 diff plus the 0.71 fifth to drop RPM and get some better economy. Anyone else care to weigh with their experiences and why I'm seeing 10 mpg lower in the Giles car. Shouldn't it be the other way around?
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Swap the pumps and injectors over as a 'heart and lungs' transplant keeping their timings identical, and see if the economies swap, or remain with the vehicles.
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2X... Lots of differences between your two test subjects and so a heart-and-lungs transplant is the best approach scientifically.
You don't mention timing, but even if it is the same it will actually be quite different due to the big difference in breaking pressure. Pump wear may be different as well...which also impacts real-world timing.
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Nothing has worse aerodynamics than a convertible...
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cabbys are heavy, theres no roof to use as structure, so they put all the structure in the pan.
weigh both cars, report back..
i bet the actual weight will shed light on things..
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Also too, not sure if you changed the 5th gear in your ACH and AGS transmission, but they both have a 0.75 fifth gear, not 0.71.
Tire size will change the RPM at a given speed too.
Does your Giles pump smoke bad under a heavy load? I noticed on mine I had to turn down the full load stop screw some. It was really pumping out the soot at 3/4 throttle or so going down the road. Thats just wasted energy going out your tailpipe.
All in all, Giles has said more than once that with his pumps, your economy should be the same if not improved, as long as you aren't trying to put out a cigarette butt on the floor board when you drive it. :)
I noticed too you're using 155 bar injectors with Merc nozzles in your stock setup. I'm no injector guru, but your setups aren't similar enough to do an accurate economy comparison, imho.
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Obviously this is not scientific because there are way to many variables and not enough controls, but just for rough comparisons with engines with the same displacement, gearing, and driving on similar chassis I would not expect a variance of 20-25% biased in one direction. I'm ruling out aerodynamics since the two cars have very similar CdA's and the fact that there isn't a whole lot of difference at the speed that I'm driving.
I'm going to start looking for an ASF or ACN trans, pop in a 0.71 fifth and improve my highway cruising and see if that does anything. With the added torque of the Giles setup and cruising at 60 mph, I wouldn't think this would be a problem. I'll swap out the IP and injectors before I do that though. When it gets to be spring and I'm not losing so much heat to ambient, I guess I should see an increase to the 50 mpg range in the Cabby.
The thing that I'm very intrigued by is the injectors. My Golf with the stock IP, 155 bar injectors w/ mercedes nozzles runs cleaner, quieter, and smoother than the hydraulic lifter Giles set up of the Cabriolet. I replaced the head gasket in this golf recently and examined the internals by using the merc nozzles; absolutely pristine and no carbon build up. Just wiped it down with a rag. Imagine that.
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The only way to keep variances the 'same' is to do as I said in post #2.
There is no substitute, period.
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Also too, not sure if you changed the 5th gear in your ACH and AGS transmission, but they both ahve a 0.75 fifth gear, not 0.71.
Tire size will change the RPM at a given speed too.
Does your Giles pump smoke bad under a heavy load? I noticed on mine I had to turn down the full load stop screw some. It was really pumping out the soot at 3/4 throttle or so going down the road. Thats just wasted energy going out your tailpipe.
All in all, Giles has said more than once that with his pumps, your economy should be the same if not improved, as long as you aren't trying to put out a cigarette butt on the floor board when you drive it. :)
I noticed too you're using 155 bar injectors with Merc nozzles in your stock setup. I'm no injector guru, but your setups aren't similar enough to do an accurate economy comparison, imho.
difference between .71 and .75 is about 40 rpm @ 70 mph..
and the merc nozzles, and 155 bar injectors could be some reason..
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I was simply pointing out he indicated he had a .71 fifth, when the AGS/ACH has a .75. The difference in RPM at 70 is actually around 160. Probably not enough to notice a huge difference.
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I would like to point out your losses as a fault of the merc nozzles. They have been proven to not work well with our precups (injector spray points the wrong way, doesn't atomize properly). So less efficiency right there.. Meaning you inject more fuel to get the same performance from them.
Why run merc nozzles? Last I checked there wasn't a shortage of the proper nozzles designed for these cars.. Lol
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I would like to point out your losses as a fault of the merc nozzles. They have been proven to not work well with our precups (injector spray points the wrong way, doesn't atomize properly). So less efficiency right there.. Meaning you inject more fuel to get the same performance from them.
So, in other words there should be an even larger discrepancy? Remember, the Merc nozzles are on the car getting the BETTER economy and running smoother (despite being solid lifter vs hydraulic).
As for the 5th gear, I swapped both of them out to be 0.71:1.
Don't get me wrong, I don't think there's anything the matter with the Performance Diesel stuff; it's absolutely awesome. I'm just skeptical at this point about getting significantly better economy over stock. Getting below 50 MPG makes me cry.
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Sorry about that, I misread the post when I replied on my phone.. You sincerely have a weird scenario.. LoL
I get 49-51 in my N/A with 60% being hwy and most of that at or above 115km/h
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i get 48mpg with NO OVER DRIVE..
GC trans .91 4th gear, 3.89 final drive..
this thing just HUMMS going down the road.
i think i got better mileage with my 4A tho, it had .70 4th gear, and a 3.94 final drive.
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Not to mention the difference in 5mpg is the teensiest (yup teensiest) amount. I'd be glad with anything over 35 for a combined city/highway/WOT romps
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The differences are confusing, but could it be something simple like the wrong thickness HG on the Gilesified engine?
What temp t-stat does each one have? Does one have more belt-ran accessories than the other?
Also alignment, tire pressure, dragging brakes and thick bearing grease will make a difference and some tires have a higher rolling resistence too.
Right now I'm in the low 30s, that's partly due to the cold but strangely this is my lowest for the last 4 years while last summer was my highest at 46-48mpg :-\.
I could handle getting your mileage. ;D
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What temp t-stat does each one have?
Good point. My mileage went up 3mpg by replacing a thermostat that wasn't quite closing all the way.
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whats each one timed at?
they shouldnt be timed the same, not with one having 135s and the other engine having 155s.. the one with the merc nozzles should get slightly more initial timing.
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whats each one timed at?
they shouldnt be timed the same, not with one having 135s and the other engine having 155s.. the one with the merc nozzles should get slightly more initial timing.
Giles pump is at 0.95mm, BOSCH pump is at 1.00mm. Tire pressures are both at the sidewall max (44 psig). Both have the same amount of belt accessories, both have new 87C thermostats, both have new wheel bearings, etc etc. (I do agree that operating temp has a significant influence on fuel consumption, emissions, and carbon build up). Although the alignment of the cabriolet is out a little bit...Like I said, this is not at all scientific but just for thumb in the air estimates, it seems a little odd. Obviously there are plenty of out there that disagree. If I ever got less than 40 MPG in one of these IDI NA engines, I'd do a full-on TDI swap. Making only 70 lb.ft. of torque and getting 30s MPG is ludicrous.
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I'm no expert by any means, but I do know Giles recommends 0.95mm/.037in advance, when using 130 bar injectors. He told me if for whatever reason you are using 150/turbo injectors to use the advance spec specified for the turbo motor.
I don't have my bentley in front of me (Im at work, saving lives ;)) but isn't turbo spec timing advance 1.05mm?
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whats each one timed at?
they shouldnt be timed the same, not with one having 135s and the other engine having 155s.. the one with the merc nozzles should get slightly more initial timing.
Giles pump is at 0.95mm, BOSCH pump is at 1.00mm. Tire pressures are both at the sidewall max (44 psig). Both have the same amount of belt accessories, both have new 87C thermostats, both have new wheel bearings, etc etc. (I do agree that operating temp has a significant influence on fuel consumption, emissions, and carbon build up). Although the alignment of the cabriolet is out a little bit...Like I said, this is not at all scientific but just for thumb in the air estimates, it seems a little odd. Obviously there are plenty of out there that disagree. If I ever got less than 40 MPG in one of these IDI NA engines, I'd do a full-on TDI swap. Making only 70 lb.ft. of torque and getting 30s MPG is ludicrous.
the giles pump has 155 bar right?
and the bosch has 135 bar right?
your timing is backwards.. thats why one car gets better mileage.
should set your timing based on the break pressures of your injectors..
155bar open later then 135 bars..
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whats each one timed at?
they shouldnt be timed the same, not with one having 135s and the other engine having 155s.. the one with the merc nozzles should get slightly more initial timing.
Giles pump is at 0.95mm, BOSCH pump is at 1.00mm. Tire pressures are both at the sidewall max (44 psig). Both have the same amount of belt accessories, both have new 87C thermostats, both have new wheel bearings, etc etc. (I do agree that operating temp has a significant influence on fuel consumption, emissions, and carbon build up). Although the alignment of the cabriolet is out a little bit...Like I said, this is not at all scientific but just for thumb in the air estimates, it seems a little odd. Obviously there are plenty of out there that disagree. If I ever got less than 40 MPG in one of these IDI NA engines, I'd do a full-on TDI swap. Making only 70 lb.ft. of torque and getting 30s MPG is ludicrous.
the giles pump has 155 bar right?
and the bosch has 135 bar right?
your timing is backwards.. thats why one car gets better mileage.
should set your timing based on the break pressures of your injectors..
155bar open later then 135 bars..
ROR
I think you've mixed the pressures up:
87 Cabriolet w/ diesel conversion:
Hydraulic lifter engine
Giles IP
Giles 135 BAR injectors
Stock 1.8 gasoline exhaust with Cat. delete
AGS transmission w/ 0.71 fifth, 3.94 diff (2500 RPM @ 60 mph)
Stock wheels/tires 175 tire width
85 Golf 1.6 NA (2-door)
Solid lifter engine
Stock BOSCH IP
155 BAR injectors w/ Merc nozzles
Stock 1.6 NA exhaust
ACH transmission w/ 0.71 fifth, 3.94 diff (2500 RPM @ 60 mph)
81 Rabbit steel wheels 155 tire width
Why should a 'Giles pump need to be advanced to 0.95 for 130 bar, but remain standard for turbo spec [155 bar]?
However, as it stands, swapping the whole lot and keeping the timing with the swap, will remove/compile all the variables and show the effect of the different bodies, assuming the engines are of similar condition... After doing this you will see which pump is tuned for economy better, or the results will give identical results [unlikely]
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yup, mixed it up..
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I'm also not convinced that coasting out of gear saves fuel. These un-throttled diesels don't have the same pumping losses of a gas engine with closed throttle. You might decrease frictional losses in the trans, but during overrun, if the pump is adjusted properly, no fuel is injected. If you are coasting in neutral, then you are burning fuel to idle the engine. I doubt the frictional losses of the trans gears is more than the burned fuel to idle the engine.
They were better than gas engines of the time, but they still have (http://www.box.net/shared/enkmtq7l2j) pumping losses. They're low displacement, so load tends to be high most of the time, especially given how people drive these days, but if someone is driving along at a moderate speed or on a large enough downhill slope it can be more efficient to operate the engine periodically at higher loads even w/ idle fuel consumption of ~.33gph in between. Like most things it depends on the specifics.
overdrivegear, I think you should try swapping the wheels/tires between the two before swapping over the whole drivetrains. Rolling resistance can vary widely between different tires and even between the same type of tire depending on wear.
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Wow im having the same problem with my 91 Jetta coupe and 81 Caddy. Both have 1.6 NA's and my Caddy gets 50mpg+ and the absolute best i have done in my Jetta with all hwy driving is 47. I did notice however that my Caddy is geared differently then my Jetta and it obviously weighs less than the Jetta but that shouldnt seem to matter at a constant rate like on the freeway. The Caddy definitely revs less on the hwy too and the gears seem to be farther apart than the Jetta's.
Now im new to the actual gear ratio thing but im slowly learning.
I am in the process of trading a MKII vr6 for a low mileage MKII Jetta 1.6na with ~100k on the motor and a yr old Giles pump. Now the Giles pump on the motor was built to "performance" specs according to the owner which concerns me due to possible lower mpg for the sake of power. I dont care about power, thats what vr6's are for. But when i Emailed Giles about the rebuilt pump he replied that the mpg will improve due to the motor working less to maintain the same speed. So im in the same boat and will be watching this thread closely
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In your case it probably is a transmission difference causing a mileage difference since the 90s IDI diesels were a bit wound up IIRC.
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In your case it probably is a transmission difference causing a mileage difference since the 90s IDI diesels were a bit wound up IIRC.
Anyone know of any good sites to research what gearbox ratio's came in what cars ect.
Sry for the highjack :-\
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In your case it probably is a transmission difference causing a mileage difference since the 90s IDI diesels were a bit wound up IIRC.
Anyone know of any good sites to research what gearbox ratio's came in what cars ect.
Sry for the highjack :-\
From my memory, scirroco.org/gears also the faq has links to all this good info.
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When i Emailed Giles about the rebuilt pump he replied that the mpg will improve due to the motor working less to maintain the same speed.
As always, hearsay can be thoroughly misconstrued, but that doesn't make any sense to me. Steady state cruising requires a specific amount of power. The engine will work exactly that "hard" to maintain that speed regardless of what pump and injectors are fitted. If instead he said that he has significantly improved overall engine efficiency then it might make sense.
Sorry this is the email i received.
"Hi
no it will make it better, since you have more Torque and HP then you can drive the car easier and still get the same speed.
Giles
From: [email protected]
Sent: Friday, February 04, 2011 4:30 PM
To: [email protected]
Subject: VW Diesel pump"
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Maybe he's referring to the retarded timing given factory advance and ULSD?
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thought i'd give my 2 cents in this equation
swapping the pump and injectors would be the best way for sure.
other things to consider are compression of both motors and the fact one motor is solid lifters and one hydraulic
i personnly don't like the Merc nozzless, they have a straight pre-stream of raw fuel in the middle of the atomized
spray pattern. it was developed just for the bad running Merc 5 cyl. with a good DNOSD293 or 273 nozzle stock
nozzles it should run much better. i have tried these nozzles in my own car and they smoked all time.
sometimes there is just something different in MPG between engines and cars that no-one can put their finger on.
my own personal car is a 93 Passat with an AAZ, Giles pump (of course). ported head, 2.5in exhaust. stock european
i/c'er. k&n filter. 135HP at the wheels. 1/4mi of 15.9sec.
this is my daily driver and i drive fast, 80-90mph all the time. lots of races and i get 43-45mpg, engine is pretty fresh
30,000mi on my own rebuild.
i see some people who get better mpg than others with the exact same car and equipment and no rhyme or reason
to say why he gets more than the next guy. would like to see the results after the complete swap
Giles
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I'm going to throw a couple thoughts in here, but I fall into the group of people suspecting non-motor causes.
When were the wheels on the caddy last checked for balance? I can't vouch for the truth of it, but I was taught years a go that an unbalanced wheel at 70mph could waste over 5hp.
Also, you have mentioned that the alignment on the caddy is a little out. I think you would be surprised by how much power is required to scrub one or more tires, even just a tiny bit. Think about trying to maintain a steady speed through a corner, you have to roll into the throttle a little, right? Consider that misalignment can be just like always trying to turn just a little bit.
I would think that either factor above could cost you at least a few mpg.