3200 rpm spring?
04-13-2007, 07:19 AM
#17
Thanks for the response. I appreciate the help.
The photos make sense to me now, thanks.
I understand the relationship between stretching the spring and the force it applies on the governor. It would seem if you could get enough travel you could make the 2600 rpm spring have as much pressure as the 3200 rpm (from the example you used a 10 inch pound spring at 1.5 inches would approximate the spring force of a 15 inch pound spring at 1 inch of travel).
I was looking at my high idle screw last night and I was able to back it out a lot more from where it was when I set it at 3100 rpm. I got an additional ~30 degrees of rotation on the accelerator lever. The screw could go back more but my accelerator pedal in the jeep hits the floor board at this point (which could be modified by adjusting the cable). I'll have to play a little bit this weekend and see if stretching the governor spring further helps the hp keep rising above 2600 rpm or if it's still flat.
Question: If the hp is still flat above 2600 rpm would this indicate that I'm being limited by the ability of the injectors to flow enough fuel?
The photos make sense to me now, thanks.
I understand the relationship between stretching the spring and the force it applies on the governor. It would seem if you could get enough travel you could make the 2600 rpm spring have as much pressure as the 3200 rpm (from the example you used a 10 inch pound spring at 1.5 inches would approximate the spring force of a 15 inch pound spring at 1 inch of travel).
I was looking at my high idle screw last night and I was able to back it out a lot more from where it was when I set it at 3100 rpm. I got an additional ~30 degrees of rotation on the accelerator lever. The screw could go back more but my accelerator pedal in the jeep hits the floor board at this point (which could be modified by adjusting the cable). I'll have to play a little bit this weekend and see if stretching the governor spring further helps the hp keep rising above 2600 rpm or if it's still flat.
Question: If the hp is still flat above 2600 rpm would this indicate that I'm being limited by the ability of the injectors to flow enough fuel?
Some of the pics in the FAQ were taken with a pump off the engine just for clarity's sake. There is no need to remove the pump, all I do is retard the timing all the way (loosen the mounting nuts and bolt and rotate the top of the pump away from the engine). This gives more room to work.
The reason a governor spring does what backing out the high idle screw doesn't is this:
Springs are rated in pounds per inch of deflection. Say your 2600 RPM spring takes 10 lbs per inch to pull it apart, and the throttle travel is enough to pull it one inch before you adjust the high idle. This hypothetical spring has 10 lbs of force available to oppose the governor. OK, so we back the high idle screw all the way out and get up to 1.25" of travel - now the spring has 12.5 lbs of force against the governor.
But the 3200 RPM spring is a lot stiffer, we'll say 15 lbs/inch to make the math simple. With the stock high idle setting, you now have 15 pounds opposing the governor, and when you back it out you have 18.75 lbs opposing the governor. This means that the governor has to spin much faster to generate the force needed to defuel the engine.
With the stiffer spring the engine would not defuel until 3200 RPM and would continue to make power up to that point.
Does that clear things up?
You can get the spring from your local Bosch pump shop. Check the yellow pages for places with names like "Diesel Fuel Injection of (your town here)" or "Yourtown Fuel Injection".
Nice rig.
The reason a governor spring does what backing out the high idle screw doesn't is this:
Springs are rated in pounds per inch of deflection. Say your 2600 RPM spring takes 10 lbs per inch to pull it apart, and the throttle travel is enough to pull it one inch before you adjust the high idle. This hypothetical spring has 10 lbs of force available to oppose the governor. OK, so we back the high idle screw all the way out and get up to 1.25" of travel - now the spring has 12.5 lbs of force against the governor.
But the 3200 RPM spring is a lot stiffer, we'll say 15 lbs/inch to make the math simple. With the stock high idle setting, you now have 15 pounds opposing the governor, and when you back it out you have 18.75 lbs opposing the governor. This means that the governor has to spin much faster to generate the force needed to defuel the engine.
With the stiffer spring the engine would not defuel until 3200 RPM and would continue to make power up to that point.
Does that clear things up?
You can get the spring from your local Bosch pump shop. Check the yellow pages for places with names like "Diesel Fuel Injection of (your town here)" or "Yourtown Fuel Injection".
Nice rig.
04-13-2007, 02:46 PM
#18
O.K. I just ordered me one of the 3200 RPM governor springs from PDR. Check my assumption and see if I am on the right track. From reading this thread, it appears to me that because the 3200 rpm spring is stiffer than the stock spring and puts more pressure to the governor, if you had two trucks lined up side by side with all the settings the same except the governor spring and mash the throttle to the same spot the truck with the 3200 rpm spring would give you more power than the stock spring? In a sense, the 3200 rpm spring gives you more power with less throttle? Am I even close to being on the right track here? Thanks!
04-13-2007, 03:22 PM
#19
Adminstrator-ess
Thanks for the response. I appreciate the help.
The photos make sense to me now, thanks.
I understand the relationship between stretching the spring and the force it applies on the governor. It would seem if you could get enough travel you could make the 2600 rpm spring have as much pressure as the 3200 rpm (from the example you used a 10 inch pound spring at 1.5 inches would approximate the spring force of a 15 inch pound spring at 1 inch of travel).
I was looking at my high idle screw last night and I was able to back it out a lot more from where it was when I set it at 3100 rpm. I got an additional ~30 degrees of rotation on the accelerator lever. The screw could go back more
but my accelerator pedal in the jeep hits the floor board at this point (which could be modified by adjusting the cable). I'll have to play a little bit this weekend and see if stretching the governor spring further helps the hp keep rising above 2600 rpm or if it's still flat.
Question: If the hp is still flat above 2600 rpm would this indicate that I'm being limited by the ability of the injectors to flow enough fuel?
The photos make sense to me now, thanks.
I understand the relationship between stretching the spring and the force it applies on the governor. It would seem if you could get enough travel you could make the 2600 rpm spring have as much pressure as the 3200 rpm (from the example you used a 10 inch pound spring at 1.5 inches would approximate the spring force of a 15 inch pound spring at 1 inch of travel).
I was looking at my high idle screw last night and I was able to back it out a lot more from where it was when I set it at 3100 rpm. I got an additional ~30 degrees of rotation on the accelerator lever. The screw could go back more
but my accelerator pedal in the jeep hits the floor board at this point (which could be modified by adjusting the cable). I'll have to play a little bit this weekend and see if stretching the governor spring further helps the hp keep rising above 2600 rpm or if it's still flat.
Question: If the hp is still flat above 2600 rpm would this indicate that I'm being limited by the ability of the injectors to flow enough fuel?
The stock spring will still defuel at about the same RPM despite your high idle tweaking. You just can't get enough extra "pull" to make a big difference in the defuel point. With the high idle screw backed out all the way, you can get it to free-rev to 3800 or so, but it will still lay down at 26-2700 RPM. A stiffer governor spring is the only way to move the defuel point significantly.
Injectors will not change this either, it will just pull harder to 2600 RPM and then lay down on you.
O.K. I just ordered me one of the 3200 RPM governor springs from PDR. Check my assumption and see if I am on the right track. From reading this thread, it appears to me that because the 3200 rpm spring is stiffer than the stock spring and puts more pressure to the governor, if you had two trucks lined up side by side with all the settings the same except the governor spring and mash the throttle to the same spot the truck with the 3200 rpm spring would give you more power than the stock spring? In a sense, the 3200 rpm spring gives you more power with less throttle? Am I even close to being on the right track here? Thanks!
04-16-2007, 09:46 AM
#20
My measurements confirm what you are saying. The accelerometer data shows that even though I've backed the high idle screw out substantially further it doesn't help the hp above ~2600 rpm. The hp still flattens out at ~2600 rpm. It doesn't seem to defuel at this point, but the power just stays flat from 2600 to 3k where I release the fuel pedal. The boost also stays high up to this point.
When you say your 5.9 VE pumps defuel above 2600 rpm with the stock spring even when backing out the high idle screw do you actually see the boost dip? Does the hp dip? Or does it just flatten out like I'm seeing (boost and hp stays constant above from ~2600-3000 rpm).
With the 3200 rpm spring does the boost and hp continue to climb above 2600 rpm, or does it keep the boost and hp from falling in the 2600-3200 rpm range?
When you say your 5.9 VE pumps defuel above 2600 rpm with the stock spring even when backing out the high idle screw do you actually see the boost dip? Does the hp dip? Or does it just flatten out like I'm seeing (boost and hp stays constant above from ~2600-3000 rpm).
With the 3200 rpm spring does the boost and hp continue to climb above 2600 rpm, or does it keep the boost and hp from falling in the 2600-3200 rpm range?
There's not enough room in the pump for you to get the travel you'd need to have the same effect as a 3200 RPM spring. It really makes a huge difference in how the engine responds to the accelerator pedal - it's worth it just for that. The stiff spring gives you more control over the fuel.
The stock spring will still defuel at about the same RPM despite your high idle tweaking. You just can't get enough extra "pull" to make a big difference in the defuel point. With the high idle screw backed out all the way, you can get it to free-rev to 3800 or so, but it will still lay down at 26-2700 RPM. A stiffer governor spring is the only way to move the defuel point significantly.
The stock spring will still defuel at about the same RPM despite your high idle tweaking. You just can't get enough extra "pull" to make a big difference in the defuel point. With the high idle screw backed out all the way, you can get it to free-rev to 3800 or so, but it will still lay down at 26-2700 RPM. A stiffer governor spring is the only way to move the defuel point significantly.
04-16-2007, 11:05 AM
#21
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Whether it keeps pulling higher depends on other fuel settings, but normally it allows you to pull hard all the way to 3200rpm or more. I have backed out of mine at 3600, still pulling hard, still accelerating, 30psi boost.
When the engine "falls on its face," it does just that. You are accelerating, and pulling hard, gaining speed, big grin on your face, then it's like someone squeezes off the fuel supply- you hit x rpm, and it stays there. It'll stay there all day, but getting much higher requires a great deal of patience. i have noticed a little more (maybe 150-200rpm) extra on a pump flowing 50% over stock when completely backing out the high idle screw.
The 366 spring makes a HUGE difference. Since your engine is a 3.3 liter, (smaller bore and stroke, I'd assume), you might do some research and see if it'd rev even higher, though if you have the set up you like, you may have n no need to do so.
Daniel
When the engine "falls on its face," it does just that. You are accelerating, and pulling hard, gaining speed, big grin on your face, then it's like someone squeezes off the fuel supply- you hit x rpm, and it stays there. It'll stay there all day, but getting much higher requires a great deal of patience. i have noticed a little more (maybe 150-200rpm) extra on a pump flowing 50% over stock when completely backing out the high idle screw.
The 366 spring makes a HUGE difference. Since your engine is a 3.3 liter, (smaller bore and stroke, I'd assume), you might do some research and see if it'd rev even higher, though if you have the set up you like, you may have n no need to do so.
Daniel
04-16-2007, 12:58 PM
#22
Thanks for the response.
I've looked at the bore and stroke of this engine compared to some others. Still have the data at my desk so I'll list them below:
Engine...............bore x stroke(mm x mm).........bore/stroke.........torque peak rpm..........hp peak rpm
Cummins 5.9: 102.1 x 119.9 .8515 ~1600 ~2900
Cummins 6.7: 107 x 124 .863 ~1600 ~3000
Cummins 3.3: 95 x 115 .8261 ~1600 ~2600
VM 2.8 (jeep liberty): 94 x 100 .94 ~1800 ~3800
VW 1.9: 79.5 x 95.5 .832 ~1900 ~3750
The 3.3 has the longest stroke relative to its bore of any of these diesel engines. My understanding is that this would tend to make it more of a low reving engine. However, the VW TDI is almost as low of ratio but it revs quite high (of course it has lighter internal parts).
I've looked at the bore and stroke of this engine compared to some others. Still have the data at my desk so I'll list them below:
Engine...............bore x stroke(mm x mm).........bore/stroke.........torque peak rpm..........hp peak rpm
Cummins 5.9: 102.1 x 119.9 .8515 ~1600 ~2900
Cummins 6.7: 107 x 124 .863 ~1600 ~3000
Cummins 3.3: 95 x 115 .8261 ~1600 ~2600
VM 2.8 (jeep liberty): 94 x 100 .94 ~1800 ~3800
VW 1.9: 79.5 x 95.5 .832 ~1900 ~3750
The 3.3 has the longest stroke relative to its bore of any of these diesel engines. My understanding is that this would tend to make it more of a low reving engine. However, the VW TDI is almost as low of ratio but it revs quite high (of course it has lighter internal parts).
Whether it keeps pulling higher depends on other fuel settings, but normally it allows you to pull hard all the way to 3200rpm or more. I have backed out of mine at 3600, still pulling hard, still accelerating, 30psi boost.
When the engine "falls on its face," it does just that. You are accelerating, and pulling hard, gaining speed, big grin on your face, then it's like someone squeezes off the fuel supply- you hit x rpm, and it stays there. It'll stay there all day, but getting much higher requires a great deal of patience. i have noticed a little more (maybe 150-200rpm) extra on a pump flowing 50% over stock when completely backing out the high idle screw.
The 366 spring makes a HUGE difference. Since your engine is a 3.3 liter, (smaller bore and stroke, I'd assume), you might do some research and see if it'd rev even higher, though if you have the set up you like, you may have n no need to do so.
Daniel
When the engine "falls on its face," it does just that. You are accelerating, and pulling hard, gaining speed, big grin on your face, then it's like someone squeezes off the fuel supply- you hit x rpm, and it stays there. It'll stay there all day, but getting much higher requires a great deal of patience. i have noticed a little more (maybe 150-200rpm) extra on a pump flowing 50% over stock when completely backing out the high idle screw.
The 366 spring makes a HUGE difference. Since your engine is a 3.3 liter, (smaller bore and stroke, I'd assume), you might do some research and see if it'd rev even higher, though if you have the set up you like, you may have n no need to do so.
Daniel
04-16-2007, 04:01 PM
#23
Registered User
Hey TDI, does your turbo have a wastegate? Generally, when a pump starts to defuel, boost falls off...but, if the pump is fueling, say, 10psi over the wastegated setting, as fueling falls off, the boost will stay the same untill it drops below the wastegate actuator's preset.
04-16-2007, 04:20 PM
#24
Registered User
ok, crappy video, but...I start in second, watch the boost and tach when I run through 3rd--you'll see the boost fall off while rpms are going up. This is with a non wastegated housing and a stock governor spring. (and a mildly tuned truck...no laughing, guys
) I wish I had a WG housing video for comparison, but you get the idea. The 3200 spring simply moves that defuel point up, as has already been said...and makes the engine a lot more fun to drive
) I wish I had a WG housing video for comparison, but you get the idea. The 3200 spring simply moves that defuel point up, as has already been said...and makes the engine a lot more fun to drive
04-16-2007, 04:53 PM
#25
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I wouldn't want to wind it up past 3500 without the HD valvesprings. I think it's very possible that it would make good power up to 4000 RPM with the right spring and enough timing.
04-16-2007, 05:23 PM
#26
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[QUOTE=wannadiesel;1457307]The reason a governor spring does what backing out the high idle screw doesn't is this:...<edit>...Does that clear things up?...<edit>...
Great explanation, Dave, it certainly does clear it up for me, as I had wondered nearly the same thing. Now I do still have one remaining question: How would the addition of the spring affect power/performance BEFORE the max rpm de-fueling occurs? Seems most drivers are reporting better throttle response/power right from idle with the spring, and your very clear explanation addresses the high rpm limit issue, so is there as obvious an explanation for it to provide different power/fuel settings when LESS than max rpm? Or could it be most all of them did the starwheel/other mods along with? Whew! Hope that isn't as confusing to everyone else as it is to me(and I wrote the dang thing!). ;-) My basis for asking is I don't think I'd be interested in the actual higher rpm, at this point never planning to exceed the 2500 limit anyways(I drive slow...but steady!!), but am interested in better off-idle and mid-range performance, and of course any possible fuel efficiency gained in the process. So I wanted to determine if the 3200 spring alone would be worthwhile for any reason other than raised rpm limit. Thanks for your time...(Is this called hijacking a thread, so I shouldn't be doing it, and post a new question instead?)
Great explanation, Dave, it certainly does clear it up for me, as I had wondered nearly the same thing. Now I do still have one remaining question: How would the addition of the spring affect power/performance BEFORE the max rpm de-fueling occurs? Seems most drivers are reporting better throttle response/power right from idle with the spring, and your very clear explanation addresses the high rpm limit issue, so is there as obvious an explanation for it to provide different power/fuel settings when LESS than max rpm? Or could it be most all of them did the starwheel/other mods along with? Whew! Hope that isn't as confusing to everyone else as it is to me(and I wrote the dang thing!). ;-) My basis for asking is I don't think I'd be interested in the actual higher rpm, at this point never planning to exceed the 2500 limit anyways(I drive slow...but steady!!), but am interested in better off-idle and mid-range performance, and of course any possible fuel efficiency gained in the process. So I wanted to determine if the 3200 spring alone would be worthwhile for any reason other than raised rpm limit. Thanks for your time...(Is this called hijacking a thread, so I shouldn't be doing it, and post a new question instead?)
04-16-2007, 05:28 PM
#27
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Now I do still have one remaining question: How would the addition of the spring affect power/performance BEFORE the max rpm de-fueling occurs? Seems most drivers are reporting better throttle response/power right from idle, and your very clear explanation addresses the high rpm limit issue, so is there as obvious an explanation for it to provide different power/fuel settings when LESS than max rpm? Whew! Hope that isn't as confusing to everyone else as it is to me(and I wrote the dang thing!). ;-) My basis for asking is I don't think I'd be interested in the actual higher rpm, at this point never planning to exceed the 2500 limit anyways(I drive slow...but steady!!), but am interested in better off-idle and mid-range performance, and of course any possible fuel efficiency gained in the process. Thanks for your time...(Is this called hijacking a thread, so I shouldn't be doing it, and post a new question instead?)
O.K. I just ordered me one of the 3200 RPM governor springs from PDR. Check my assumption and see if I am on the right track. From reading this thread, it appears to me that because the 3200 rpm spring is stiffer than the stock spring and puts more pressure to the governor, if you had two trucks lined up side by side with all the settings the same except the governor spring and mash the throttle to the same spot the truck with the 3200 rpm spring would give you more power than the stock spring? In a sense, the 3200 rpm spring gives you more power with less throttle? Am I even close to being on the right track here? Thanks!
04-16-2007, 05:36 PM
#28
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Ok...let me try to say where I will understand(but most others will probably say 'HUH?')...you mean there will be no actual 'gain' of power by fueling more in the low/mid throttle, it would simply, by increased tension against the governor, 'hold' the position better in a way to make the same pedal travel 'appear' to cause more power? End result being a 'lighter' pedal pressure would seem like 'more power'? So in other words(isn't that what I just did...other words...what's wrong with that guy?), as I don't plan excess rpm, the spring would be virtually no benefit to me, right? On the other hand, the starwheel adjustment WILL affect low/mid throttle response by actually changing fuel pin position up/down the offset cone shape, correct? And thanks for the info and being patient with me, as usual! ;-)
04-16-2007, 06:18 PM
#29
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I wouldn't say there's no benefit - the truck is much nicer to drive with a 3200 RPM spring. It no longer feels like there's a bungee cord in the throttle linkage.
But you are correct that it does not change the actual fueling curve.
But you are correct that it does not change the actual fueling curve.
04-16-2007, 07:11 PM
#30
Registered User
This post from efbeason contains the answer to your question.
The stiff spring gives you more control over the fuel. The truck feels more powerful, but it really isn't. You will not gain mileage from this, the fact that you are using less "pedal" to go a given speed is deceptive. You are still using the same amount of fuel, but the stiffer spring means you don't have to push down on the pedal so hard to overcome the governor. Getting clearer?
The stiff spring gives you more control over the fuel. The truck feels more powerful, but it really isn't. You will not gain mileage from this, the fact that you are using less "pedal" to go a given speed is deceptive. You are still using the same amount of fuel, but the stiffer spring means you don't have to push down on the pedal so hard to overcome the governor. Getting clearer?