Discussion
Mark,
The engine draws little power from the vac pump (the S1 doesn't have any vac pump at all). It is primarily to power the brake booster and heater/ac controls.
Since the mods you're doing don't affect these, I'd stay w/ the belt driven pump. It will last much longer and you'd have to supply a fused electrical circuit to power the electric one anyway.
If you're replacing the belt driven pump, the NAPA replacement is #64-1006, about $110 + core. Happy Motoring! Jim'85TE
The engine draws little power from the vac pump (the S1 doesn't have any vac pump at all). It is primarily to power the brake booster and heater/ac controls.
Since the mods you're doing don't affect these, I'd stay w/ the belt driven pump. It will last much longer and you'd have to supply a fused electrical circuit to power the electric one anyway.
If you're replacing the belt driven pump, the NAPA replacement is #64-1006, about $110 + core. Happy Motoring! Jim'85TE
lotusguy said:
Mark,
The engine draws little power from the vac pump (the S1 doesn't have any vac pump at all). It is primarily to power the brake booster and heater/ac controls.
Since the mods you're doing don't affect these, I'd stay w/ the belt driven pump. It will last much longer and you'd have to supply a fused electrical circuit to power the electric one anyway.
If you're replacing the belt driven pump, the NAPA replacement is #64-1006, about $110 + core. Happy Motoring! Jim'85TE
Jim,
The idea was less for getting more power and more for getting the thing out of the way (case and point I had to take it off again last night to get to the water-pump), it just kind of "sticks out" there and gets in the way. As I couldn't find a replacement I decided to stick with the one I have anyway.
Thanks for the info. on the NAPA replacement though.
Cheers,
Mark
Following on from my recently found obsession for getting rid of my vacuum pump; here is (what no doubt will prove to be) a silly question: Why didn’t Lotus use the inlet manifold pressure for vacuum like many other vehicle manufacturers? I can only think of a few possible reasons:
1. There is not enough vacuum produced by the inlet manifold.
2. The manifold vacuum becomes positive under boost.
3. They didn’t want “gunk” sucked through the vacuum pipes to get in to the inlet manifold.
4. They just like sticking stuff on their engines that makes all other parts really difficult to get to at repair time and hence-forth keep their mechanics in business.
5. Some other reason that I missed.
Multiple choice folks, any ideas?
Thanks,
Mark (88 Turbo)
1. There is not enough vacuum produced by the inlet manifold.
2. The manifold vacuum becomes positive under boost.
3. They didn’t want “gunk” sucked through the vacuum pipes to get in to the inlet manifold.
4. They just like sticking stuff on their engines that makes all other parts really difficult to get to at repair time and hence-forth keep their mechanics in business.
5. Some other reason that I missed.
Multiple choice folks, any ideas?
Thanks,
Mark (88 Turbo)
Hi,
"And the Winner is.....
#1 - There is not enough vacuum produced by the inlet manifold.
On the S1 Esprits, Lotus did not add a supplementary vacuum pump. But, with the advent of uprating the brakes and the heating/cooling system in later models, they found the 9XX engine produced insufficient vacuum to meet these demands.
Consequently, they added the belt driven vacuum pump you have. This pump was originally spec'd from GM (even prior to GM's ownership of Lotus). The General had created this pump to provide vac power to their line of Diesel engined passenger cars in the late '70's and '80's (Diesel's are notorious for their inability to produce a lot of vacuum). Happy Motoring!...Jim '85TE
"And the Winner is.....
#1 - There is not enough vacuum produced by the inlet manifold.
On the S1 Esprits, Lotus did not add a supplementary vacuum pump. But, with the advent of uprating the brakes and the heating/cooling system in later models, they found the 9XX engine produced insufficient vacuum to meet these demands.
Consequently, they added the belt driven vacuum pump you have. This pump was originally spec'd from GM (even prior to GM's ownership of Lotus). The General had created this pump to provide vac power to their line of Diesel engined passenger cars in the late '70's and '80's (Diesel's are notorious for their inability to produce a lot of vacuum). Happy Motoring!...Jim '85TE
AZ88Turbo said:
Following on from my recently found obsession for getting rid of my vacuum pump; here is (what no doubt will prove to be) a silly question: Why didn’t Lotus use the inlet manifold pressure for vacuum like many other vehicle manufacturers? I can only think of a few possible reasons:
1. There is not enough vacuum produced by the inlet manifold.
2. The manifold vacuum becomes positive under boost.
3. They didn’t want “gunk” sucked through the vacuum pipes to get in to the inlet manifold.
4. They just like sticking stuff on their engines that makes all other parts really difficult to get to at repair time and hence-forth keep their mechanics in business.
5. Some other reason that I missed.
Multiple choice folks, any ideas?
Thanks,
Mark (88 Turbo)
Hi Jim,
I figured the reason would be something like that, however; was this mostly because of the other things (engine management etc.) that needed to constant vacuum? After doing some more research (I know, I need to get a life) it seems as though there may be ample vacuum to run just the breaks (that and the heater flap are the only things that use vacuum on my car now the TEC3 is controlling everything else). The breaks only need about 10 in-hg to run effectively (Lotus specifies 18 in-hg/40 kPa absolute for the whole vacuum system on an 88 model) and from what I understand they don’t need that in “real-time”, the servo stores up vacuum via use of the non-return valve whenever it gets it. Looking at a datalog from running my car; the kPa is below 40 most of the time when I am not under boost. Sooooo……… would there be enough to run just the breaks I wonder?????????
Not sure but I guess the real question is: am I crazy enough to test out the theory??? Who knows, maybe!
Mark (88 Turbo)
I figured the reason would be something like that, however; was this mostly because of the other things (engine management etc.) that needed to constant vacuum? After doing some more research (I know, I need to get a life) it seems as though there may be ample vacuum to run just the breaks (that and the heater flap are the only things that use vacuum on my car now the TEC3 is controlling everything else). The breaks only need about 10 in-hg to run effectively (Lotus specifies 18 in-hg/40 kPa absolute for the whole vacuum system on an 88 model) and from what I understand they don’t need that in “real-time”, the servo stores up vacuum via use of the non-return valve whenever it gets it. Looking at a datalog from running my car; the kPa is below 40 most of the time when I am not under boost. Sooooo……… would there be enough to run just the breaks I wonder?????????
Not sure but I guess the real question is: am I crazy enough to test out the theory??? Who knows, maybe!
Mark (88 Turbo)
Mark.
I guess I'm at a loss to understand why you're so insistent on swimming upstream on this issue.
There isn't any appreciable advantage to running w/o the vacuum pump, but much potential disadvantage to doing so. If this were a viable option, many would have already figured this out and eliminated it, or Lotus would not have added it in the first place. If performance gains are your goal, larger inhectors, lightened flywheel, bigger Turbo, ported heads and larger valves will yield much more positive results.
Ask yourself what price you put on having a back-up should the servo diaphram split or the check valve fail? Sure, these may be one in a million circumstances (actually probably more like one in thousands), but do you want to risk being the one?? Also, considering the size or more appropriately, the volume of the Brake Servo, how quickly will manifold vacuum alone recharge it..?? W/o the vacuum line hooked up, you get about one good application of the brakes before the vacuum in the servo is exhausted, ask me how I know...!!
It's really a form of benign, cheap insurance following the old addage- You can't have the Go without the Whoa..."
It isn't that much of an impediment to performing other work on the car, and it doesn't add appreciable weight, so my suggestion is to stick with it. Conversely, you can always remove it, drive the car (preferrably w/o me in it), and see what you think. Happy Motoring!...Jim'85TE
I guess I'm at a loss to understand why you're so insistent on swimming upstream on this issue.
There isn't any appreciable advantage to running w/o the vacuum pump, but much potential disadvantage to doing so. If this were a viable option, many would have already figured this out and eliminated it, or Lotus would not have added it in the first place. If performance gains are your goal, larger inhectors, lightened flywheel, bigger Turbo, ported heads and larger valves will yield much more positive results.
Ask yourself what price you put on having a back-up should the servo diaphram split or the check valve fail? Sure, these may be one in a million circumstances (actually probably more like one in thousands), but do you want to risk being the one?? Also, considering the size or more appropriately, the volume of the Brake Servo, how quickly will manifold vacuum alone recharge it..?? W/o the vacuum line hooked up, you get about one good application of the brakes before the vacuum in the servo is exhausted, ask me how I know...!!
It's really a form of benign, cheap insurance following the old addage- You can't have the Go without the Whoa..."
It isn't that much of an impediment to performing other work on the car, and it doesn't add appreciable weight, so my suggestion is to stick with it. Conversely, you can always remove it, drive the car (preferrably w/o me in it), and see what you think. Happy Motoring!...Jim'85TE
Jim,
I know and agree with what you are saying. I guess all the trouble I have had with the water-pump has meant that I have had to keep removing the vacuum pump. I'm waiting for parts right now so it is sat on my bench. I just keep looking at it and wondering "why", that's all (gives me something to research). I realize that there would be no power advantage to getting rid of it (non noticeable now I have the rest of the stuff done anyway). I don't think there is any harm in "thinking out of the box" once in a while.
I have in the meantime found an electric booster pump that could be used to supplement the manifold vacuum when needed, it only runs when the pressure in the servo drops below 11 in-hg and stops when it gets to 18 in-hg and only takes 2 amps of power when running. Not sure that I am going to go with it as it is about $100 but it was interesting learning about the possibilities.
Thanks for your input,
Mark (88 Turbo)
I know and agree with what you are saying. I guess all the trouble I have had with the water-pump has meant that I have had to keep removing the vacuum pump. I'm waiting for parts right now so it is sat on my bench. I just keep looking at it and wondering "why", that's all (gives me something to research). I realize that there would be no power advantage to getting rid of it (non noticeable now I have the rest of the stuff done anyway). I don't think there is any harm in "thinking out of the box" once in a while.
I have in the meantime found an electric booster pump that could be used to supplement the manifold vacuum when needed, it only runs when the pressure in the servo drops below 11 in-hg and stops when it gets to 18 in-hg and only takes 2 amps of power when running. Not sure that I am going to go with it as it is about $100 but it was interesting learning about the possibilities.
Thanks for your input,
Mark (88 Turbo)
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