944 S2 MAF Sensor Kit

[Thom]

a radio frequency ablation of my right heart atria to cure an a-flutter rythmn.

How long did you suffer from this and which conditions triggered the flutter and how often?

Just curious as I went through the same op 6 months ago which went trouble free and this has changed my life for the better, so to speak. When the first flutter happened whilst I was under intense stress as a student there was no technology to cure this and I had just been told to take things easy, quit coffee and alcohol (yeah right ).

I am sure you will enjoy the MAF as much as I loved the SciVision MAF on my ex S2. The significant improvement in throttle response tranformed the car and made it far more enjoyable on fast drives.

[Latitude48]

a radio frequency ablation of my right heart atria to cure an a-flutter rythmn.

How long did you suffer from this and which conditions triggered the flutter and how often?

Just curious as I went through the same op 6 months ago which went trouble free and this has changed my life for the better, so to speak. When the first flutter happened whilst I was under intense stress as a student there was no technology to cure this and I had just been told to take things easy, quit coffee and alcohol (yeah right ).

I am sure you will enjoy the MAF as much as I loved the SciVision MAF on my ex S2. The significant improvement in throttle response tranformed the car and made it far more enjoyable on fast drives.

I can't say how long I had been having the AFlutter (AFL), which is flutter in the upper atria, as I was completely asymptomatic, so it could have been up to a year since my last checkup. Eleven years ago I had an ablation for SVT. SVT was very noticeable as my heart rate would go up to something like 200 and then calm down. I was semi-awake for that ablation but completely sedated for this one. I have yearly checkups with my cardiologist. My last one was on September 18, and that's when the AFL showed up on the ECG. I wore a CAM monitor for two weeks and it came back as 100% AFL (no A-Fib, which was good). Like A-Fib, AFL can cause little blood clots, so I've been on the anticoagulant Eliquis since September 20, and may have to stay on it permanently. I have a slow heartrate when resting, typically under 40 bpm, so my Apple watch is always bugging me, ha, ha. So far, no pacemaker has been needed though as my rate goes up normally with exersion. I do drink two cups of coffee per day and up until a month ago I typically drank two glasses of wine or beer per day. Now, zero.

Glad you got your SciVision MAF to work as it never worked correctly on my S2 when I tried it in 2006. I'm looking forward to getting the Storch VE installed.

[Thom]

Ok, I had to look up the differences between A-fib and ATL. I had A-fib.
It was frustrating to skip workshop activity for almost a month but well worth it. My heart rate has always been in the average and always stayed the same during each episode. Anyway, good luck with the recover.

Keep us updated with how the MAF works.

[Britmat]

However, it could be awhile before I get this insalle... like no working in an engine compartment, ha, ha.

Completely understandable. Take it easy to rest and heal properly. There’s nothing worse than going “too big, too soon” and having setbacks that prolong the situation.

[cda951]

This looks like a well-made kit, but a major reason to install a hot-film MAF kit in place of an AFM (aside from the obvious elimination of a moving part and its wear-prone electrical wiper circuit) is to reduce the restriction in airflow, especially with a turbocharged application. From my understanding this restriction is NOT from the spring-loaded flapper itself (Bosch test data showed a minuscule pressure drop from this), but from the relatively small rectangular slot required for the AFM flapper. One can see the difference in cross section between the rectangular inlet and circular outlet in the last photo of each of the MAF units on the PLJ site.

I do not intend to disparage what appears to be a very high-quality product, and I understand the reason for retaining the rectangular slot to enable bolt-on capability for factory airboxes---though the MAF kit would still cause the car to fail German TÜV if I am not mistaken.

As for normally aspirated 944/S/S2 applications, this restriction doesn't amount to much, and all else equal there is likely to be a performance improvement if everything is properly calibrated. The 944S2 "quadrate" intake manifold is a fine-tuned thing from the factory, so a cone filter and full 3" MAF could affect things . . . .

Also, a proper cold-air intake----as ALL Porsche factory airboxes are---and the attendant reduction in IAT is likely to outweigh the restriction in an otherwise stock 944 NA application versus a dumb cone air filter sucking in hot air from the engine bay with a true 3" inlet in many cases. Porsche went to great lengths to stuff the 944S2 airbox behind the nose panel to ensure this, and went further with the extra intake temp sensor at the base of the intake plenum to activate the radiator fans if need be.

All this said, I'd go with the proven Vitesse setup for a 951 with higher boost levels and especially one with a larger turbocharger.

[Tom]

This looks like a well-made kit, but a major reason to install a hot-film MAF kit in place of an AFM (aside from the obvious elimination of a moving part and its wear-prone electrical wiper circuit) is to reduce the restriction in airflow, especially with a turbocharged application. From my understanding this restriction is NOT from the spring-loaded flapper itself (Bosch test data showed a minuscule pressure drop from this), but from the relatively small rectangular slot required for the AFM flapper. One can see the difference in cross section between the rectangular inlet and circular outlet in the last photo of each of the MAF units on the PLJ site.

I do not intend to disparage what appears to be a very high-quality product, and I understand the reason for retaining the rectangular slot to enable bolt-on capability for factory airboxes---though the MAF kit would still cause the car to fail German TÜV if I am not mistaken.

As for normally aspirated 944/S/S2 applications, this restriction doesn't amount to much, and all else equal there is likely to be a performance improvement if everything is properly calibrated. The 944S2 "quadrate" intake manifold is a fine-tuned thing from the factory, so a cone filter and full 3" MAF could affect things . . . .

Also, a proper cold-air intake----as ALL Porsche factory airboxes are---and the attendant reduction in IAT is likely to outweigh the restriction in an otherwise stock 944 NA application versus a dumb cone air filter sucking in hot air from the engine bay with a true 3" inlet in many cases. Porsche went to great lengths to stuff the 944S2 airbox behind the nose panel to ensure this, and went further with the extra intake temp sensor at the base of the intake plenum to activate the radiator fans if need be.

All this said, I'd go with the proven Vitesse setup for a 951 with higher boost levels and especially one with a larger turbocharger.

Do you have any links or sources where Bosch confirmed the barn door is not a meaningful restriction? That's been a topic of much speculation for years, and I've never seen real data either way. On the other hand, I can 'see' the restriction/limits caused by the size of the opening...

Plus 1 on the @Fast951/Vitesse MAF. In addition to less flow restriction, it allows you to measure more air flow. The stock AFM reaches max voltage somewhere in the 300-330 range from what I can tell. You can fudge the WOT fuel and 'skate to the puck' for a bit more than that, but if you want to control fuel accurately above that range, you need something other than the factory AFM to measure the incoming air.

[cda951]

Do you have any links or sources where Bosch confirmed the barn door is not a meaningful restriction? That's been a topic of much speculation for years, and I've never seen real data either way. On the other hand, I can 'see' the restriction/limits caused by the size of the opening...

Plus 1 on the @Fast951/Vitesse MAF. In addition to less flow restriction, it allows you to measure more air flow. The stock AFM reaches max voltage somewhere in the 300-330 range from what I can tell. You can fudge the WOT fuel and 'skate to the puck' for a bit more than that, but if you want to control fuel accurately above that range, you need something other than the factory AFM to measure the incoming air.

Hi Tom,

It's in this Bosch fuel injection book, long out of print. Page 6 of Chapter 3:

[johnb]

...

It's in this Bosch fuel injection book, long out of print. Page 6 of Chapter 3:

Actually I just bought this from Amazon the other day and it looks brand new. I think it's still in print.

[Tom]

Do you have any links or sources where Bosch confirmed the barn door is not a meaningful restriction? That's been a topic of much speculation for years, and I've never seen real data either way. On the other hand, I can 'see' the restriction/limits caused by the size of the opening...

Plus 1 on the @Fast951/Vitesse MAF. In addition to less flow restriction, it allows you to measure more air flow. The stock AFM reaches max voltage somewhere in the 300-330 range from what I can tell. You can fudge the WOT fuel and 'skate to the puck' for a bit more than that, but if you want to control fuel accurately above that range, you need something other than the factory AFM to measure the incoming air.

Hi Tom,

It's in this Bosch fuel injection book, long out of print. Page 6 of Chapter 3:

That's awesome, thank you!! I have that book too -- time to re-read it I guess. I'll definitely file that away for the next time someone says the barn door is 'the' big restriction.

[O875]

As for normally aspirated 944/S/S2 applications, this restriction doesn't amount to much, and all else equal there is likely to be a performance improvement if everything is properly calibrated. The 944S2 "quadrate" intake manifold is a fine-tuned thing from the factory, so a cone filter and full 3" MAF could affect things . . . .

In the case of the SVE unit, since it simply replaces the AFM but everything else remains, would you expect an improvement for the S2, given that fine-tuned intake? I like the idea of keeping all the sensible intake elements but wonder if the intake might be upset or enhanced by the PLJ unit.