IXLR8

It is wired directly to the battery as a voltmeter monitoring battery voltage should be wired, and because it draws less than 2 mA, it can be wired "always-on", in other words not "switched".

The voltmeter is held to the carpet using the "hook" portion of Velcro. It works well enough to keep the meter in pace during normal street use. No holes were drilled and no factory wiring was cut.

Voltmeter Install in a 993

Surface Mount Datel LCD Voltmeter Install

rol607

Per recommendations from fellow RL'ers, I put the Inrestate MTP-91 in my 993 this past Wednesday. Direct fit with center vent.

jo-hans

I know this tread is a year old ..... but last week I replaced my Optima with an Interstate MTP-91. Just not happy with the life of the Optima's.
The MTP-91 has the odd oval vent on the battery so the 993 vent tube/elbow won't fit - I am sure I can modify something that will work but I read about a vent tube kit from Interstate. I suppose I can contact interstate and ask for the kit.
Not so direct fit without the kit.

AOW162435

I installed an MTP-91 about 6 years ago - no issues to date. If the battery does not come with the rubber vent tube, Interstate will snd one out for free.


Andreas

IXLR8

I have seen a short piece of thin-wall rubber hose used between the vent and the OEM clear vinyl hose. The rubber hose slips over the vent on the battery and the vinyl hose slips into the rubber hose. You can always use miniature tie-wraps to apply some extra pressure at both joints.

Another possibility if the vinyl hose almost slips over the battery vent is to use a heat gun to soften the vinyl allowing it to stretch/deform...do not aim the heat gun at the battery.

NC TRACKRAT

Just a reminder that Sam's now stocks the DURACELL 48 which is made by and identical to the East Penn. Price last week was $84.95.

tommyg

Re: battery vent tube. I re-routed mine from the fender cavity to out one of the drainage holes under the spare, so if it pukes it goes out of the car.

jo-hans

Thanks guys - I will contact Interstate first.

And Tommy - I had the same thought to run the drain into a grommet at the bottom like you did. We are talking fumes though so up or down don't matter - I'll probably just use the existing hose that goes into the fender.
I see the bolt for the FPB but is that another drain right next to it or the wire for your neon lights?

jo-hans

I dropped by an Interstate dealer locally and they gave me two bags.




The label inside brought back memories mentioning the Merkur XR4Ti. I used to own one back in 1985 when they first came out. You either liked it or hated the look. I never ended up putting that much needed Rapido Intercooler on......
Anyways - I decided to trim the end of the 'L' as indicated on the reverse of the label (Fig.B) so it was snug to the battery case. Also the clamp on the + terminal would not fit and I had to cut some of the protruding white plastic of the battery case (rim) to allow the downward shaped clamp to fit properly on the terminal.

BobbyT

Alex,
You have a PM.

Dr. No

I'm reviving this thread because it has the most respondents who may be able to comment.

My OEM Porsche battery (in the car when I bought it 7 yrs ago) just pooped out after a cold evening with my dome lights on because the frunk popped open. It would still light the lights and run the radio, but I just got clicking when attempting to start. I was hoping it was just the battery after doing some searches here. Tried to revive it with my CTEK 330 to no avail.

Got an Interstate MTP-48, also after searching here, to install myself. Fit great and car starts like a champ now (thank God and Rennlist) but there were some issues:

1. The vent tube was not connected to the OEM Porsche battery that was in the car. I'm also missing the black L-shaped part that connects the vent port on the battery to the plastic vent tube that runs into the fender. See here for a good pic:

https://rennlist.com/forums/6486795-post1.html

Vent is on the side of the MTP-48 battery, like the OEM. I now know to source this from Interstate - after I couldn't find the part or the vent tube in the PET - but also figured I could survive for a bit without it given that I had been driving for seven years without it hooked up.

2. When I went to swap out the old battery for the new, my owner's manual said to disconnect the negative, grounded terminal first. Problem is that the positive terminal is the grounded one, as I've noticed from others' posts here too. WTF Porsche? Wasn't sure what to do but managed not to explode anything or electrocute myself. Whew.

3. I used my OEM trickle charger during the battery change process (which took about 30 minutes due to need to go in the house a couple of times and consult Rennlist and PET when I ran into the vent tube which then wouldn't fit in the battery vent) and did not lose any of my radio or other codes.

All in all, glad to have the car running again and the learning experience for the price of a battery. And thanks to RL for enough information to give me the confidence I wouldn't blow up my car.

JPS

Mine leaked at the track. Sprayed acid down the side of the car. Bought an Optima that afternoon. Never going back. Had to replace the stone guard and another piece of clear bra, and I need to take it in to get a little buffed. Oh, and get a wheel refinished too.

Mike J

Huh? Maybe we need to talk about the definition of "grounded". To me, the grounded line is the one attached to the chassis, on the 993 it's clearly the one that is a bare copper braided line, and is the one that is farthest away from the front of the car, and attaches to the -ve of the battery. The nearer line to the front of the car, with a rubber sleeve covering the conductor, is connected to the +ve, and is the "live" wire.

How does this differ from what you are discussing?

BTW, I hate Optima batteries, had two of them, both failed prematurely, and did not like them. Give me a cheap lead-acid battery anytime, more cost effective and less problems.

Cheers,

Mike

Cactus

+1

Slow Guy

Dr. No, are you sure you don't mean Interstate MTP-91 (not MTP-48)?

Only old British cars are Pos (+) ground (OK, I know it's not entirely true but for the most part it is), certainly not Porsche 993.

The reason for disconnecting neg (-) first is in case your wrench touches the frame/body of the vehicle while you're removing the pos (+) terminal you won't get an arc (and potential explosion) if the neg. (-) has already been removed. You do the opposite when reconnecting the battery, connect the pos (+) first, then the neg. (-).