So after a little bit of digging it turns out that G/S MAF measurement gives a relatively good HP Estimate
This is what I found on the net
N/A and Turbo Engine HP= MAF (g/s) * 1.25
Supercharged Engine HP=MAF (g/s) *1.1
N/A and Turbo Dynojet WHP manual= MAF (g/s) * 1.1
Supercharged Dynojet WHP manual =MAF (g/s) *0.95

Using the 1.1 ratio I get 420 hp flywheel hp or 362 at the wheels on Dynojet
wow just as my car stock hp rating

Please share your results!

 

Seems kind of close to reality...

I've seen peaks of ~360 g/s on my XJR, according to these figures i'd have 396hp at the crank or 342hp at the wheels.

Plausible!

Although they note "manual" which should have less drivetrain losses than an automatic.

 

Interesting, I don't have a record of MAF but my SAE corrected baseline on a calibrated Dynojet was around 361 (I'll have to pull it up to double check) however I have always discounted dyno numbers because I have always been lead to believe they are only valid in before and after comparisons.

 

It is indeed a good indication, I have also used this myself in the past to check tuning progress. At least you can see if you have made progress when it comes to airflow modifications, however it doesn't take any inefficiencies into consideration.

You need to have a good odbii meter, preferably the IDS as it takes more measurements per second. Without the IDS, make sure you only select the MAF sensor for reading, that gives about 6 measurements per second, and next the higher the gear to more precise it becomes (ie 3rd was always ideal, but fast).

 

Just an Update
went to 397 G/S on a entrance ramp , translates into 436 flywheel hp
Anyone else have numbers to compare?

 

UPDATE:
so I tested the maf into hp calculator on my other car, 2000 Mercedes e55 AMG (stock hp rating 349hp) my car has cats removed and intake modifications
got 284 G/S max which translates into 355hp which is very darn close to what it should be
Thumbs up !!

 

Finally had a moment to try it on mine, but only a moment. In automatic DS mode the highest read was 332 g/s at 5034 RPM & 52mph. Hope to try again in manual mode to see if I can get higher numbers.

 

Alex are you taking the measurements in 3rd as Avos suggested if not , which gear are your measurements taken at .

 

You got to floor it all the way to redline

It doesn't seem to make a difference 2nd vs 3rd gear
I put car in manual mode switch into 2nd and floor at at around 2800rpm all the way red line without switching gears, car will do it for you so dont worry.

 

It actually does, at least when you want a good reading. Its simple, in 1 second you spawn a big rpm range in 2nd compared to 3rd. Only the IDS is relatively fast enough in measurements per second to use 2nd gear, but even then.

 

Redline in 3rd for me is 180kmh / 110mph, I'll be thrown in jail if I get caught doing that on the street here...

If you only have Torque available, then set up the screen to only record one measurement, the MAF rate. The more measurements you have going the slower the refresh rate.

 

If that's the case, then I may not be able to do it around here. I'd never get to 110 in the city whether safe or legal. I'd have to find a bit of freeway without getting caught.

I was using dash command and recording gear, speed and rpm but could set it to just MAF.

 

Ah I was talking about the XJR, in the XKR it would be like 155kmh / 95mph to redline in 3rd, or thereabouts. Still a problem for me that's an instant loss of license here...

 

Attached is an old example (probably done in Germany), when my car was still stockish in 3rd gear (4.0 gearbox, so 4,31 final gear ratio). You see that 5000 to 6000 rpm took about 5.2 seconds. Have no idea what odbii reader I used then, but you can see roughly 6 recordings per second.

A 2nd gear for a 4.2 car with a ZF6HP gearbox, has a final gear ratio of about 7,75 and am not sure what speed range that will give you, but I would guess from 5000 to 6000 rpm would be done in maybe 2 seconds or so? That means much less granularity pending on the device you use to record.

So bottom line is that of course you can use only 2nd gear, certainly if it’s just a fun reading, but if you want to use it to see if you make any improvements in airflow, you need more granular readings if you see what I mean.

So just do a recording, and as Cambo mentioned only select the MAF to get the best readings in a low gear.

 

I had a quick play in my '07 XKR while I was out and about last night and the peak seems to have been 374.

I will have to try again with fewer metrics being captured and add RPM.

 

The exact same numbers shown for 1.6 seconds ? Seems like you've missed a lot of data there...

 

It was trying to capture 14 different metrics so I might have been swamping it. 374 actually spans from 01:47.6 to 01:49.8 in the original spreadsheet and the numbers either side are 194 and 27 so it is no where near as granular as the one avos posted.

I will try again and see if I can get some more meaningful figures.

 

Took it to the freeway and in manual mode let it shift on its own at 6500 rpm. Only reading MAF the highest number I got from 2-3 and 3-4 was 383 and times 1.1 that's 421. Did the tune and pulley not have any impact on the numbers then?

 

Maybe not, it depends on the tune.

There are a number of limiters in the PanPag PCM which could negate the peak HP effects of a pulley, if they aren't addressed then yeah, peak MAF numbers may not be higher than stock.

For example there is one limiter "Maximum load" which is an upper limit of the volume of air coming in to the engine, if this value is reached the PCM starts to close the throttle, that value needs to be raised in the tune or you will hit the ceiling, so to speak...

 

I have tried it once again today in 2nd and in 3rd and there was only a 5 g/s difference between , so I think its much safe just to do it in 2nd gear at least with my OBD adapter.
Im using torque pro app with a cheap Amazone bluetooth adapter. In torque app make sure to select highest refresh rate, I think its 12times/second.