Cheap Performance Meter

[Rusty]

Just had a look at the data and I'm really impressed. Had a play on Excel and calculated the power for a Golf GT TDI 150 at around 150bhp using a guess of 20% losses. I'll get some proper data and then make an excel spreadsheet up to use as a template with all the calculated fields in it. Looking forward to getting some data from das Audi soon.

[A80Avant]

by the way,i will be getting a cheap g-tech used soon so next time will be with proper weight of the car + both performance box and g-tech pro rr to compare.

Basically im not sure if the rr can do it's own accel runs like the PB,but at least it can provide a better power curve which is what the PB is missing.

if you need any info for your excel let me know

[Rusty]

You can calculate power from the raw data if it's missing. That's what all the equations are at the top of this thread. For second gear I'd ignore air resistance, for 3rd/or 4th I'll have to caluclate it and see what sort of contribution it makes. For a car as powerful as yours it'll make less contribution compared to my mere 300bhp

[A80Avant]

on a 4th gear pull mine has about 67hp air drag according to the gtech air drag calculator..on 2nd gear its 16hp so even that makes a bit of a difference,but you can always add that at the end,right?

[S2central.net]

Just FYI - I found a roadtest article in a book I just bought... comparing last of UR (20V) against one of the first S2 Coupes in UK. It was quoting factory figs as Cd of 0.32 for the S2 and 0.45 for the UR20V...

[Rusty]

Yeah, for the coupe I've been using 0.32 and A of 1.89. I'v quite enjoying getting into the maths behind the figures. Time to look at the GPS acceleration data next and see how that is done. Then I can either do a sort of equation of motion from say GPS data or can have confidence in the data supplied by racechrono. Nothing like some algebra followed by some number crunching to keep the grey matter nice and dustfrei!

[20V-Fever]

im not sure if u know but the apple iphone has a realy good performance meter
the software im using now enables you to plug it into your odb II port and shows everything from intake temp to exhaust even coolant temps and such g meter quater mile times etc

[Rusty]

Yeah thanks, I did know that but I don't have an iphone and I don't want to spend £200 on an itouch. I think the iphone isn't available on all networks over here either. If you've got a iphone then you've got a good cheap way of getting data! Good to know the maths behind the numbers and what affects the data.

[20V-Fever]

well the software and the cable to plug into the phone is about 40 us dollars or so

[Rusty]

I've now got some data to play with. It's pretty messy so I've got to massage it a bit to get something meaningful at the mo. It's still quite new so it'll be a little while before it's straight in my head.

[Rusty]

Here are some second gear runs, start speed is 35mph to limiter. Not done on particularly level ground or on the same bit of road but still quite close. Was quite a fun run to the shops for once

[Rusty]

Getting the hang of this now. Went out with a mate and did several runs in his S4, I then analysed the data and the results are great. Of the runs 1 was erroneous and 6 were fine. I used 5 runs and calculated 30-60 times. These ranged from 2.88 to 2.96s with most around 2.89 and an average of 2.90s! This data will be used to identify the gains of an FMIC setup on the S4 this weekend.

Really chuffed with the data, it's super smooth and with the GPS in a better position (dash) it got strong signal for all but 1 run.

Here's the data:-

[Billman]

can you make the equations on KM/h so we can check it with other systems like Powerbox or G-Tech?

[S2central.net]

The one BIG advantage you have with this method Andy over something like my GTech RR is being able to get meaningful results like 30-60, 50-70 times... None of this 'perfect launch' and standing starts on a pure G-meter. That makes it really easy for you to quantify gains from things like FMIC upgrades and whatever else.

I'll get the spare ECU back to you some time soon - for some objective data from your GPS gizmo on the T-Stream & V-Stream if you are up for it... I'll have a map switcherooni on it for ease of comparison. Then no doubt you'll wanna play with the X-Stream and a big fat WG spring when I have that ready.

Meantime I do need to get my own *** into the cold weather for some GTech results on the T-Stream & V-Stream.

[EspenW]

The one BIG advantage you have with this method Andy over something like my GTech RR is being able to get meaningful results like 30-60, 50-70 times... None of this 'perfect launch' and standing starts on a pure G-meter. That makes it really easy for you to quantify gains from things like FMIC upgrades and whatever else.

Can't you get 30-60 etc from your speed vs. time graphs in the PASS software?