SirLapsalot

I think that is probably the best location for the sensor as it's also not subjected to heat soak in the intake manifold during hot restarts or long park idles. TMAP is great to get both pressure and temperature in one sensor at the intake manifold, but for fueling control, directly before the TB is probably best. Current after market standalones still offer solutions for the TMAP in the manifold concern with heat soak in the form of additional compensations, so it's not as much of a problem as it used to be. Current OEM's often actually have all three, TMAP in the intake manifold, charge air temp sensor in the charge pipe between intercooler and throttle body, and intake air temperature at the MAF.

jimbo1111

Im in the process of building an afm that is capable of fueling using 80lb injectors. I have already figured out the temp sensor and proper cfm calibration. I first started working on replicating the original afm and its currently at the cnc machinist. It will be a drop in replacement for the original. The added benefit is that its going to be non restrictive, as im using a state of the art sensor to capture air volume.
Once completed I will keep it 100% open source for those wanting to build there own. There is really no market and im doing it as a hobbist.
No fancy chips will be needed, as the dme is familiar with the signal. In the 80lb injector model a tune will be necessary. I figured its a good time to let the community know.

Droops83

Indeed, I will be experimenting with a TMAP sensor in the J-boot to see if a "cold air" intake is worth it in a turbocharged application (it certainly is for an NA engine). VEMS is pretty basic and doesn't have a ton of extra sensor inputs/outputs, but there are enough to do some experimentation and logging with a temporary sensor (such as pre-intercooler, etc).

Porsche and most OEMs are using plastic intake manifolds (with the TMAP sensor usually mounted in the manifold just downstream of the throttle body), which aren't quite as prone to heat-soaking as in a metal manifold, but the tightly packed engine bays make for high temperatures in there (hence the rather large fans under the decklid of a 991/992, for example). Of course, there is an engine compartment temp sensor to activate the fans, which means the same data can be used as an input to compensate for heat-soak in the MAT as you mention.

SirLapsalot

Nice! I am doing something similar I guess (pic below). I don't have data on my 944 yet, however based on past experience - While there are still a few variables to consider, in general, a decrease in the inlet temperature to the turbo will definitely carry across to the post intercooler temps. So you should be able to realize an improvement. Maybe we could compare notes later on!

Yep that's a good point, the plastic manifolds don't hold heat like aluminum did but still a concern I suppose. Although I was kind of referring to heat soak effects in a transient situation where you may still be using a compensation based on hotter air than what is actually being ingested due to air in the intake manifold used to start the compensation. However, mechanical heat soak of the thermistor from being mounted on a hot intake manifold seems like a legitimate concern too.

Example of the former would be the heat soak in an idle/low speed situation after driving off or during a tip-in, where the acceleration enrichment can be difficult to get perfect if also using intake air temperature compensation from your TMAP in the manifold. Because momentarily that intake air temp being used for corrections won't jive with the accel enrichment amount if it was calibrated in a non-heat soaked condition. Also, in that case, or a short soak hot restart, most of the heat transfer is from conduction through the head, and or convection through internal EGR. Of course the engine room temperature has a large effect too, especially for a longer soak time.

This is one reason why OEM's calibrate via the MAF rather than using speed density, in addition to the increased robustness by measuring actual airflow. Some use both and switch between them depending on the situation. Maybe getting way too far away from what's possible with the 944 DME and MAF kits at this point though. Sorry.



P.S. Accordion hose was for initial testing, don't like it or necessarily trust it for long term use.

Droops83

Haha, true, but it is a good discussion.

On this topic, however, I will soon be installing a Rogue A-Tune on a customer's '89 951, so I will share my impressions of that. I am eager to experience the back-to-back difference with stock, because I had my eye on this kit for several years (mainly for California smog purposes) before taking the plunge with a standalone system.

fast951

We do use the IAT and it's part of the MAF. We have done lots of testing in this area. I'm not comfortable sharing the technical aspect on how we use the IAT, as many times we shared technical data it got used by competitors.

Years ago, we built a custom logger to simultaneously log Temps in various spots in the intake track. Customers using the Vitesse Motronic Monitor noticed there are two separate Gauges, an IAT and a VAF/MAF IAT.

Droops83

Cool, thanks, I wouldn't expect you to divulge any data like that.

944M3

Small update. I did end up purchasing the Vitesse MAF. Unfortunately it seems my wiring is faulty or my DME has an issue, I haven’t been able get the MAF to work. My plan is to replace my harness and maybe get the ftech9 DME. For now I’m back to A-Tune.

I will add that John has helped me all along my journey. I’m very grateful for the support.

Also wanted to add that this thread has a ton of good information. Re-reading the thread I realized how much I “thought” I understood. But now it a makes a lot more sense.

I was considering going to a standalone but I’ve come to my own conclusion that it would make no sense to go through the complication of a standalone in my situation, meaning a daily driver with upgraded turbo. In fact, re-reading this thread makes me wonder if the combination of MAF with MAP and our Motronic DME (as used by Vitesse’s setup) is superior to a standalone using just MAP (for my situation I’m not saying all situations) I’ve read many posts that make this statement and now I “think” I understand why, thanks to this thread (that I had to re-read to understand lol)

944M3

And WOW this thread is from 2021, geez time is flying.

Toolbelt0

I have an evergreen turbo with a 6 hot-side, A-tune, Tial waste-gate, Fabspeed exhaust. upgraded clutch, new ftech-9, a race cam and a few other things.. I really am enjoying the car at 15 lbs boost. I think its the perfect setup. I have found that anything beyond that will probably cost a fortune to get just right and the aggravation that will come along with it. might make you hate the car. My car is currently just right. I'm not sure why LR stopped selling the a-tune. Think it was a great concept. It uses a map sensor to add fuel beyond what the afm can meter.