The motor in my Squareback is due for a rebuild. It's currently getting 25 mpg, I'd like to get at least 30 mpg with it. Although it is an automatic, so it runs at slightly higher rpms. I was thinking I could duplicate the Hot VWs mileage motor with the exception of the camshaft, since I will be running the stock D-jet.
This is the list of cams in the CB Performance fuel efficient series. Would any of these be compatible with D-jet, or should I just stick with the stocker?
2229 Eagle Racing Cam - Adv. Duration 260° / Dur. @ .050" 216° / Lift @ cam .299" / Lift w/1.1:1 Rocker Arms .328"
2230 Eagle Racing Cam - Adv. Duration 264° / Dur. @ .050" 220° / Lift @ cam .301" / Lift w/1.1:1 Rocker Arms .331"
2231 Eagle Racing Cam - Adv. Duration 268° / Dur. @ .050" 228° / Lift @ cam .313" / Lift w/1.1:1 Rocker Arms .344"
2232 Eagle Racing Cam - Adv. Duration 262° / Dur. @ .050" 230° / Lift @ cam .360" / Lift w/1.1:1 Rocker Arms .396"
Type 3 mileage motor.
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Piledriver
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If you are running D-Jet, you are VERY limited as to the valve timing, as it's not really ...tunable... any overlap beyond stock can jack with it very badly, and only so much tweeking can be done.
I would look at using a very stockish cam with 1.4 rockers and such, or to putting a MS box in as a replacement brain so you can actually tune it.
The stock manifolding is great as long as you don't go too big on displacement.
If it was a T4, the Web73 was designed just for this, not sure if Web has something similar for the T1/T3.
I would look at using a very stockish cam with 1.4 rockers and such, or to putting a MS box in as a replacement brain so you can actually tune it.
The stock manifolding is great as long as you don't go too big on displacement.
If it was a T4, the Web73 was designed just for this, not sure if Web has something similar for the T1/T3.
Addendum to Newtons first law:
zero vehicles on jackstands, square gets a fresh 090 and 1911, cabby gets a blower.
EZ3.6 Vanagon after that.(mounted, needs everything finished) then Creamsicle.
zero vehicles on jackstands, square gets a fresh 090 and 1911, cabby gets a blower.
EZ3.6 Vanagon after that.(mounted, needs everything finished) then Creamsicle.
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Marc
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I once had an 88x69 motor in a `73 Squareback using a Bugpack 4061 cam (270ºadv/234º@.050"/.396"at valve w/1.1s) and was quite satisfied with the results. It had a very low compression ratio (7.15:1) and as one would expect the low end was slightly soggy with that much cam, but on the open road it had very good power and fuel economy. I had to tweak the pressure sensor to bring down the idle CO, and used an earlier SVDA distributor instead of the `73 DVDA, but otherwise the FI was all stock. It cruised easily at 70-75MPH and still gave >30MPG on cheap gas. I wouldn't hesitate to do it again, but at today's fuel prices I'd go higher on the C.R. (~8:1 or so) and run Premium - the low-end torque would be better and the cost-per-mile should be the same or even less.
Based upon that experience I'd expect the 2231 to work OK on a 1745, which would have an inherent torque advantage over a 1679. If you do more stop-and-go driving than highway the 2230 might be more sensible.
With either I'd be prepared to have to tamper with the pressure sensor, but that's not all that daunting if you have access to a CO meter. IIRC I set mine to 2-2.5%.
Based upon that experience I'd expect the 2231 to work OK on a 1745, which would have an inherent torque advantage over a 1679. If you do more stop-and-go driving than highway the 2230 might be more sensible.
With either I'd be prepared to have to tamper with the pressure sensor, but that's not all that daunting if you have access to a CO meter. IIRC I set mine to 2-2.5%.
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vwfreek
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raygreenwood
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vwfreek
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I don't know much about cams, other than being able to draw them in AutoCAD from a graph of the profile. The overlap would be the degrees between when the intake valve opens and when the exhaust valve closes, correct? The specs for the type 4 Web 73 from the website states that the intake opens at 4° before TDC and the exhaust closes at 4° after TDC, so this would be 8° of total overlap?
I found this formula in another post: "The formula for cam timing events is: Intake opening = duration divided by 2 minus the lobe center. Intake closing = duration divided by 2 plus the lobe center minus 180. exhaust opening = duration divided by 2 plus the lobe center minus 180. exhaust closing = duration divided by 2 minus the lobe center. use the duration numbers @ .050 to work the formula."
Using this formula for the 2280 Eagle which has a 107° lobe center, the intake would open 4° before TDC and the exhaust would close at 4° after TDC. Which would result in 8° of overlap. So it looks like it should work if I plugged the figures in correctly.
I found this formula in another post: "The formula for cam timing events is: Intake opening = duration divided by 2 minus the lobe center. Intake closing = duration divided by 2 plus the lobe center minus 180. exhaust opening = duration divided by 2 plus the lobe center minus 180. exhaust closing = duration divided by 2 minus the lobe center. use the duration numbers @ .050 to work the formula."
Using this formula for the 2280 Eagle which has a 107° lobe center, the intake would open 4° before TDC and the exhaust would close at 4° after TDC. Which would result in 8° of overlap. So it looks like it should work if I plugged the figures in correctly.
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raygreenwood
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Don't get too hung up in overlap with relation to D-jet....thats not the issue. Yes, you need to have reasonable lobe center to get the correct vacuum pulse and exhaust overlap, but the crucial part of a D-jet cam is the intake valve opening point. They are specific...because the injection istimed from teh distributorat a specific preset ignition timing. That being important because if your ignition timing is off or tweeked with...it changes teh injection start point ....but not the point at which the intake valves start to open.
Map teh original cam and look for one with thesame or very close intake valve opening points.Yes...D-jet can benefit from a better cam...mostly duration wise. Ray
Map teh original cam and look for one with thesame or very close intake valve opening points.Yes...D-jet can benefit from a better cam...mostly duration wise. Ray
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Marc
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To a degree; advancing the cam slightly will get the intake valve shut sooner which'll reduce reversion and improve manifold vacuum at lower speeds - but you're also changing the intake valve opening event as well as the exhaust valve timing when you do this, and that can be counterproductive if you go much beyond 2-3°.
On paper the CBPerformance cams seem to have some pretty long clearance ramps (advertised duration ~4-8° greater than other cams with the same .050"-lift duration). That could just be due to variations in measuring methods (the SAE standard uses .006" lift, but there's no univeral standard for "advertised" duration). This is why when considering cam specs you should give more weight to the .050" duration than the "advertised".
FWIW, Web-Cam rates a stock grind at 250° adv, 214°@.050", .334" lift - that implies that the #2229 Eagle is a pretty mild unit - doubtful that you'd notice any difference.
On paper the CBPerformance cams seem to have some pretty long clearance ramps (advertised duration ~4-8° greater than other cams with the same .050"-lift duration). That could just be due to variations in measuring methods (the SAE standard uses .006" lift, but there's no univeral standard for "advertised" duration). This is why when considering cam specs you should give more weight to the .050" duration than the "advertised".
FWIW, Web-Cam rates a stock grind at 250° adv, 214°@.050", .334" lift - that implies that the #2229 Eagle is a pretty mild unit - doubtful that you'd notice any difference.
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raygreenwood
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Marc is correct...only a very tiny amount can be done with cam timing....and it will not be enough to help you if you have the wrong intake valve timing for D-jet.
You can end up with an incredibly bad running car with the wrong cam and D-jet.
You really need to understand the total issue here...and this is a D-jet only issue.
The start of the injector pulse is begun by a pair of switches in the distributor. Two injectors are fired by each switch....this is important. 1/3 and 2/4 respectively.
The ideal thing would be for the injectors for each cylinder to fire right at the moment the respective intake valve for each cylinder opens.
But since they are fired in pairs......and only two switches....only two cylinders can be correctly timed.
Two of them will generally be a little behind.
What vw/Bosch actually did was to take the two cylinders that would have been timed decently close to their intake valve opening points ...and delay them slightly so they start injecting later than they should....and the two that would have been somehwere like 90* out of time would not be so far out. All four injection points are off time in D-jet...but optimized enough and centered in overlap enough to run well. At idle you actually run with two very wet ports in D-et. If have a lot of traffic driving you will see these as the two black varnished intake ports when you remove the manifolds for any reason.
yes....much has been written about the fact that once your rpm is say ....much over 1800-2000 rpm....the injection timing point means a lot less....as we are talking milliseconds here.
But ...anyone who has extensively worked with D-jet will know better.
Its easy to demonstrate. Simply remove the trigger plate from the dizzy. Slot the screw holes so you have about 15 degrees total +/- movement of the trigger plate. Re-install it in stock position. Install an accurate fuel pressure gauge. Start the car. Make sure the fuel pressure is correct and stable.
What happens next....is when you slide the trigger plate too far in one direction or the other ......at almost any rpm..... it disturbs atomization and proper fuel dosing enough on at least two cylinders....that it causes not only a change in engine output but a change in engine vacuum signature because of thatchange in output. You can literally see the affect this has on the engine...because the fuel pressure needle will start a rapid high pressure swing/oscillation....of between 5-7 psi or more. very rapid.
You can also feel this oscillation at the same ratio.....by putting your hand on the MPS.
What is happening is that the vacuum signature oscillation caused by very poor running....caused by inoportune injection point on all four cylinders....is causing the MPS to run the injection pulsewidth from maximum to minimum and back again....very very quickly. It shows up as rapidly oscillating fuel pressure.
This problem is only fully possible on D-jet. Even other map based vehicles generally don't have this issue...because they mostly use fully ganged injectors...or bank fired injectors or lately...sequential injection.
This oscillation is a combination of intake valve timing, and paired injectors....coupled with the use of the MPS.
This is important.......The way the electronics are built in the ECU....each one of the two trigger circuits cannot be armed until after the previous one has fired. One pair of injectors can fire at a time.
Also...they have a set window of duration in degrees of camshaft rotation within which they can operate.
So....in short...you need a cam whose intake valve opening point in degrees....is very similar to stock D-jet. The only way to really see this is to install the dizzy in correctly timed position...install a test light to both triggers...and turn the engine over by hand to see where in relation to valve opening point...each injector fires.
D-jet can run very very well....and yes it can be upsized and downsized to almost any degree...contrary to popular belief.....as long as (a) the cam timing (with respect to intake valve start point) or something at least close to it, .....is respected and (b) as you size up....at some point the volumetrics of the intake plenun, TB and runners must upgrade as well....so as not to upset the vacuum signature of the system.
Yes...you can use cams with slightly more lift and duration. These systems like a little more duration....but are not happy with excessive lift because it stalls velocity and messes up the vacuum signature. Along with this....the intake valve timing is specific. Ray
You can end up with an incredibly bad running car with the wrong cam and D-jet.
You really need to understand the total issue here...and this is a D-jet only issue.
The start of the injector pulse is begun by a pair of switches in the distributor. Two injectors are fired by each switch....this is important. 1/3 and 2/4 respectively.
The ideal thing would be for the injectors for each cylinder to fire right at the moment the respective intake valve for each cylinder opens.
But since they are fired in pairs......and only two switches....only two cylinders can be correctly timed.
Two of them will generally be a little behind.
What vw/Bosch actually did was to take the two cylinders that would have been timed decently close to their intake valve opening points ...and delay them slightly so they start injecting later than they should....and the two that would have been somehwere like 90* out of time would not be so far out. All four injection points are off time in D-jet...but optimized enough and centered in overlap enough to run well. At idle you actually run with two very wet ports in D-et. If have a lot of traffic driving you will see these as the two black varnished intake ports when you remove the manifolds for any reason.
yes....much has been written about the fact that once your rpm is say ....much over 1800-2000 rpm....the injection timing point means a lot less....as we are talking milliseconds here.
But ...anyone who has extensively worked with D-jet will know better.
Its easy to demonstrate. Simply remove the trigger plate from the dizzy. Slot the screw holes so you have about 15 degrees total +/- movement of the trigger plate. Re-install it in stock position. Install an accurate fuel pressure gauge. Start the car. Make sure the fuel pressure is correct and stable.
What happens next....is when you slide the trigger plate too far in one direction or the other ......at almost any rpm..... it disturbs atomization and proper fuel dosing enough on at least two cylinders....that it causes not only a change in engine output but a change in engine vacuum signature because of thatchange in output. You can literally see the affect this has on the engine...because the fuel pressure needle will start a rapid high pressure swing/oscillation....of between 5-7 psi or more. very rapid.
You can also feel this oscillation at the same ratio.....by putting your hand on the MPS.
What is happening is that the vacuum signature oscillation caused by very poor running....caused by inoportune injection point on all four cylinders....is causing the MPS to run the injection pulsewidth from maximum to minimum and back again....very very quickly. It shows up as rapidly oscillating fuel pressure.
This problem is only fully possible on D-jet. Even other map based vehicles generally don't have this issue...because they mostly use fully ganged injectors...or bank fired injectors or lately...sequential injection.
This oscillation is a combination of intake valve timing, and paired injectors....coupled with the use of the MPS.
This is important.......The way the electronics are built in the ECU....each one of the two trigger circuits cannot be armed until after the previous one has fired. One pair of injectors can fire at a time.
Also...they have a set window of duration in degrees of camshaft rotation within which they can operate.
So....in short...you need a cam whose intake valve opening point in degrees....is very similar to stock D-jet. The only way to really see this is to install the dizzy in correctly timed position...install a test light to both triggers...and turn the engine over by hand to see where in relation to valve opening point...each injector fires.
D-jet can run very very well....and yes it can be upsized and downsized to almost any degree...contrary to popular belief.....as long as (a) the cam timing (with respect to intake valve start point) or something at least close to it, .....is respected and (b) as you size up....at some point the volumetrics of the intake plenun, TB and runners must upgrade as well....so as not to upset the vacuum signature of the system.
Yes...you can use cams with slightly more lift and duration. These systems like a little more duration....but are not happy with excessive lift because it stalls velocity and messes up the vacuum signature. Along with this....the intake valve timing is specific. Ray