sooner964

I've been fighting an intermittent slow warm start-up issue for a little over a year. Along the way, I've replaced the coils, the distributor caps and rotors, and most recently, the cylinder head temperature sensor (it was throwing an occasional error in the OBD), and nothing seems to have caused the issue to go away. I've been monitoring the voltage of my battery in several different states for a few months, and I decided that with the ignition off, a reading of 12.2 VDC seemed just a bit low. My previous battery was an Interstate Megatron Pro, manufactured in 2014. For my new battery, I decided to go with an AGM (absorbed glass matt) instead of the traditional flooded type like the MTP. I considered an Interstate AGM, a Sears DieHard Gold AGM, and the Bosch Platinum series AGM Group 48/H6. I went with the Bosch because the price was good (PepBoys has a 30% discount right now), it is warranted for 48 months no-cost replacement and prorated after the initial period, and Bosch just seems right in a Porsche. I'll give the obligatory disclaimer now that I have no affiliation with any of the aforementioned companies or products.

Prior to installing the new Bosch, I checked the voltage to see what my starting baseline was. The reading I got was 12.83 VDC. With the car running at idle, it was reading around 13.5 VDC initially, and after a few minutes between idle and application of throttle between 2-3k RPM, was up to 13.8 VDC. With time, I could see that going up a bit more as the alternator charges the battery more. If I remember correctly, my old battery read around 13.4 VDC at idle.

Installation was straightforward. Life is made simple when you first remove the space saver spare tire. Then you just have to unbolt the bracket at the base of the battery (13mm), and disconnect the leads (negative first, then positive) and vent tube. The Bosch unit fits in perfectly. I had to pry open my terminal clamps a little more for the posts, as they seemed to be a bit wider than those on the previous Interstate unit. Connect the vent tube and the leads, positive then negative, and it is good to go.

Time will tell how good the battery is. Still need to run a system adaptation since the battery was disconnected, but I haven't had a chance to drive the car enough to get it up to temperature. I don't know yet if this will remediate my intermittent warm start, but at least the number of components left in the system that could be causing the issue is growing short.

Rocket Rob

I've had good luck with the Bosch batteries. I have them in both of my 964's.

creaturecat

I've had good luck with all batteries. : )

Laker

I just replaced my Interstate Megatron a few months ago. Only because it was over 7 years old and I happened to be driving by the Deka factory store. Never an issue with the old Interstate. Do you keep it on a battery tender/maintainer?

sooner964

I don't keep it on a battery tender. I drive the car almost every day so I haven't seen a need to keep it on one. Is it recommended to keep it on one, regardless?

jpar

You shouldn't need a tender if you drive it that often. The tenders are more for the garage queens like mine. As far as Bosch batteries, they're actually very good quality as the're now made by East Penn/Deka.

sooner964

? that's what I figured. I think Bosch has a solid product.