# MES-DEA vacuum pump for 97 jetta



## adiel (Sep 21, 2009)

Hello currently the MES-DEA vacuum pump comes in two flavors: It includes an electronic pressure switch (Type 70/6E relative pressure measuring sensor) or (Type 70/6E2 absolute pressure measuring sensor) that turns off the pump when the vacuum in the booster reaches a customized maximum value.

My question is which one is the correct pump model for a 1997 VW Jetta, the 6E or the 6E2? 

Thanks Before Hand,
Adiel


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## neanderthal (Jul 24, 2008)

Actually it is more important for your elevation level of where you live. Either will work like a charm in your car. But if you live in and area with high elevation, the 70/6e will make less vacuum and may never shut off.

Here is a quote from the metricmind website, a place that sells both of those vacuum pumps.


70/6E and 70/6E2 has very low acoustic noise and vibration levels, and hardly noticed during operation. The vacuum is controlled by integrated control circuitry consisting of vacuum sensor and solid state vacuum switch. The 70/6E has relative pressure switch whereas 70/6E2 has absolute pressure switch. Both types will maintain preset vacuum level cycling on and off on its own between -600mbar (17.7" Hg) and -650 mbar (19.2" Hg), however 70/6E will reduce vacuum level as atmospheric pressure drops (e.g. at high altitudes) so may never shut off. For instance, at he elevation of 4000 feet above sea level, the 70/6E may only be able to produce 15" Hg vacuum so the shutoff threshold of 19.2" HG will never be reached. In contrast, 70/6E2 will always reach 19.2" regardless of the atmospheric pressure. This needs to be considered for your application.


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## DIYguy (Sep 18, 2008)

adiel said:


> Hello currently the MES-DEA vacuum pump comes in two flavors: It includes an electronic pressure switch (Type 70/6E relative pressure measuring sensor) or (Type 70/6E2 absolute pressure measuring sensor) that turns off the pump when the vacuum in the booster reaches a customized maximum value.
> 
> My question is which one is the correct pump model for a 1997 VW Jetta, the 6E or the 6E2?
> 
> ...


Both units will likely work ok for you. I believe the main difference is that the 70/6E2 is pressure compensated. Meaning, based on atmospheric pressure, it maintains its vacuum setting. So, if you traveled a mountainous area and went way up in elevation such that atmospheric/barometric pressure dropped significantly, it would maintain the set vacuum level. 
I went with the base model.

EDIT.....ooops, sorry, when I started typing, there were no replies yet... lol


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## adiel (Sep 21, 2009)

Thanks guys, it looks like the 6E would also be fine for me since I have not seen a mountain around here.  I live in Miami, Florida.

Thanks Again,
Adiel


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## jaspersk (Jun 26, 2008)

A '97 Jetta. Cool!! I have a '95 Jetta. If you ever want to bounce any ideas off of me, feel free to email me at steveskarda (at) gmail (dot) com.

I do happen to have the MesDea vacuum pump in my car. I love that vacuum pump and was glad I paid the additional money for it. As for which switch I bought, I don't remember there being an option to buy one or the other. I thought I just bought the only version they sold. I think I remember there being an option for an additional $100 to buy a larger pump but I bought the cheaper one. Works great. 

The one thing I will say that surprised me about the pump is that it has a REALLY tight deadband on its pressure setpoint. I have what I think is a fairly large vacuum reservoir made out of PVC but the vacuum pumps still runs every time I hit the brakes. I played around with it a bit and if I crack the line even a tiny little bit the vacuum pump will kick on and cycle on/off. None of this is a problem but it surprised me since I read folks talk about how with a large vacuum reservoirs and those square d pressure switches talk about how their big noisy pumps might only turn on once every 3 or 4 times hitting the brakes. This pump is different.


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## adiel (Sep 21, 2009)

Thanks jaspersk! What exactly will the reservoir tank do? Will I be better with the reservoir tank or without it? I am trying to use up all the space I can... 

Adiel


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## jaspersk (Jun 26, 2008)

adiel said:


> Thanks jaspersk! What exactly will the reservoir tank do? Will I be better with the reservoir tank or without it? I am trying to use up all the space I can...
> 
> Adiel


It stores vacuum so if you had a pump failure, you'd still have some power brakes. How many times you could brake after loosing the pump is dependent on how big of tank you use. Theoretically it is suppose to limit how often your pump has to cycle but like I said my mes dea always cycles when I hit the brake. 

I hear you on the space. I mounted the pump in the right front fender under the main frame. I put the largest pvc piping I could fit inside the fender above the wheel. It had to go on the right side as there is already stuff on the left (or driver) side. I had to take the wheel well cover off to put it in there.

I'd be interested in hearing what others think regarding the need for a vacuum tank. I am not sure that I'd bother with it on future conversions but I'd want to find out what others think.


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## Woodsmith (Jun 5, 2008)

I am using the aircon compressor as a vacuum pump driven from the main drive motor and controlled by switching the electric clutch on the pulley.

I rigged it up to see if it produced enough vacuum to operate the servo by driving it with a mains motor and connecting it direct to the servo with a gauge in line.









The gauge read 11"hg and when the brake pedal was depressed the gauge showed a drop of 2-3"hg at each press using just the volume of the pipework. The aircon compressor was able to replenish the vacuum in the pipework within a second or two after each press.

I decided to add a reserviour using an old dry powder fire extinguisher bottle. The effect of this is that the air con compressor takes a little longer to get to full vacuum, 4-5 seconds at 700rpm, but it should slow down the cycling of the compressor and give several presses of the pedal before the vacuum is deminished. This is just an educated assumption as I don't have a drive motor yet to try it with.

This is the set up of the vacuum plumbing in the car.









The air con compressor is in the back of the car as it is mid engined car and I am using the original aircon pipe to bring the vacuum to the front of the car. The aircon pipe is large bore, around 13mm compared to 5mm for the original vacuum pipe. This will add to the size of the reserviour of vacuum. The original vacuum pipe from the engine is used to take vacuum back to the engine bay where the pressure switch will be sited for controlling the electric clutch pulley. I have also installed a vacuum gauge in the instrument panel to keep a check on the vacuum while driving.









I haven't installed a non return valve as yet. I'm not sure I need one as the aircon compressor is quite good at holding a vacuum when it isn't running so I am assuming that there is a valve in the compressor body already.

Here is a video of the test rig to see if the aircon compressor worked at all. Note the reserviour connection, made from a Bic pen tube, leaked. However, you can still see the time it takes to get to full vacuum.


I suppose one line of thought for reserviour or not is the time it take to fully evacuate the reserviour to make the servo effective.
If you have a large reserviour then it will take a longer time to get to full vacuum then it would without it.
It would then depend on the volume flow rate of the pump. A small pump and a large reserviour would mean that for the first part of the drive the pump would still be trying to reach full vacuum. A large pump without a reserviour would be able to replenish the vacuum in the plumbing almost as fast as the brakes are used.


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## adiel (Sep 21, 2009)

Woodsmith, that is a great explanation and video! I now understand how the reservoir helps hold vacuum for a longer period of time.  I did want to ask you one question, on your system you are planning on powering your vacuum pump through the motor pulley instead of electricity correct? My question is: I would not see this happening on an electric vacuum system. Lets say you are going down hill, you have the car on neutral, your motor is not spinning but you are pressing the breaks to slow down on the hill. Am I missing something or could you possibly run out of vacuum causing your vacuum light to come on? 

Adiel


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## Woodsmith (Jun 5, 2008)

adiel said:


> Lets say you are going down hill, you have the car on neutral, your motor is not spinning but you are pressing the breaks to slow down on the hill. Am I missing something or could you possibly run out of vacuum causing your vacuum light to come on?
> 
> Adiel


In the senario you give yes, the vacuum will run out. However, I have been taught to never coast in neutral as I would then 'not be in proper control of the vehicle' according to the driving manual we have over here. I would find it very uncomfortable coasting in neutral and so my natural temptation would be to leave it in gear and use the non existent engine braking. It is on that basis that I decided that I would be ok running from the drive motor.
I would be leaving the motor spinning unpowered to maintain the vacuum under gravity power.

Also, the self contained pump I bought wouldn't operate the servo so, being on a small budget, I decided to use what I had available. There is still the issue of finding the drive motor. I would need to find one that had a tail shaft and was still short enough to fit in the car.

I am also keeping my options open to return to an electric pump if I had to. In which case it would sit in the front near the servo and I would adjust the plumbing to suit.


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## jaspersk (Jun 26, 2008)

Woodsmith said:


> I have been taught to never coast in neutral as I would then 'not be in proper control of the vehicle' according to the driving manual we have over here. I would find it very uncomfortable coasting in neutral and so my natural temptation would be to leave it in gear and use the non existent engine braking.


You sort of suggested it in your post but you'll have to get comfortable coasting in neutral because there is no difference between an electrical vehicle coasting in gear and an ICE vehicle coasting in neutral. An electrical vehicle feels like it is in neutral anytime you let off the gas. 

There is a very good reason to keep your electric car always in gear however and that is motor cooling. In fact, the experienced drivers often say that us newbie's have a bad tendency to put our cars in too high a gear which keeps the rpms lower which limits cooling. However at the same time you don't want to have it in too low a gear such that you run your motor above 7000 rpm especially if you were coasting down a hill. That will destroy your commutator.

Do you really have a manual that says you are 'not in proper control of the vehicle' if your coast in neutral? That is funny.


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## adiel (Sep 21, 2009)

The coasting in neutral issue seems like an interesting topic.  I opened a thread on this issue:

http://www.diyelectriccar.com/forums/showthread.php/coasting-neutral-good-bad-37072.html

Thanks,
Adiel


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## Woodsmith (Jun 5, 2008)

jaspersk said:


> You sort of suggested it in your post but you'll have to get comfortable coasting in neutral because there is no difference between an electrical vehicle coasting in gear and an ICE vehicle coasting in neutral. An electrical vehicle feels like it is in neutral anytime you let off the gas.
> 
> There is a very good reason to keep your electric car always in gear however and that is motor cooling. In fact, the experienced drivers often say that us newbie's have a bad tendency to put our cars in too high a gear which keeps the rpms lower which limits cooling. However at the same time you don't want to have it in too low a gear such that you run your motor above 7000 rpm especially if you were coasting down a hill. That will destroy your commutator.
> 
> Do you really have a manual that says you are 'not in proper control of the vehicle' if your coast in neutral? That is funny.


Yes, quite right. In an EV it will feel just like coasting in neutral so I will have to get used to the feeling, however, the car will be in gear and so, as you say, the motor cooling is still there. Also the car will be in gear so when needed the power is tere without having to select a suitable gear first.

I'm not sure what the current driving manual says but certainly in my day it was advised against and the Highway code also says not to coast in neutral.
I was also taught to always be covering or using a least one of the pedals at all times so if not accelerating the foot should be hovering over the brake ready for action and not hovering over the accelerator.

Different countries have different driving requirements and there is a mix of good and bad in all of them I think.


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