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Premium Member
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Discussion Starter · #1 ·
Hi.

My fleet of old Porsches (the thread will be continued soon), is fitted with C7005 chips.

If I fit C8515s (G or H), on similar cars, and the whole lot raced together, will there be much discernible difference performance-wise between the two batches (purely because of the chip difference)? All chips will be as original with respect to firmware and diodes.

I imagine there would be. Is there any way I could get away with changing chips at this stage, and maintain a fair balance.

Thanks.
 

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novice jazz player &
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C7005 and C8515 rev G should deliver identical performance... same rectifier diodes and same motor/brake transistors and same control firmware.

C8515 rev H is different... Schottky rectifier diodes in place of silicon junction diodes... so less lost volts. Also, the motor and brake MOSFETs are upgraded so less on resistance. Newer firmware too.

c
 
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Circuit Owner
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To add to what Dr_C advises: The Rev H C8515 is easily recognised as it is the DPR chip WITHOUT the large silver barrel shaped capacitor on the visible side of the chip. This delivers more oomph to the motor so is best reserved for the slowest DPR car in your fleet.

You are likely to get performance variations because of tyre grip, wheelbase, track, weight in the chassis, centre of gravity and ability of the motor. Bear in mind that mass produced motors can vary by as much as 5% either side of average. The chips are the least of your problems when it coems to matching performance.

If you are really serious about balancing performance then it will be a case of swapping motors around and changing the other vairables OR, if you have a 6 car power base - using software to profile each car and tune how much power it gets and the rate of fuel consumption.

Your old 935s will be far slower than modern 997s simply because of the ground clearance, centre of gravity and motor configuration (old in-line and modern sidewinder).

You might find it easier to spend 5 minutes on each car finding out its fastest lap times and creating tiers of cars that have similar lap times for racing purposes.

Finally - if some of your vintage 935's have the old Johnson motor I am not sure whether a standard chip will drive those (if they are old and stiff they may draw too much current for the chip). The old Johnson motor is no match for the newer Mabuchi but the newer Mabuchi can be fitted with simple adaptors.
 

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Brilliant replies gentlemen which both I and my racing buddies will find most useful.

OK, so:

C7005 and C8515 G - have the same firmware, so no need to mess about trying to match throttle profiles or anything out of the ordinary. This is terrific news.

C8515 H - understood.

C8515 earlier versions and Rev H physical differences: I am already aware of. It is an interesting point you make about reserving these for the slowest car - will do.

Current fleet - we, (legal Covid bubble), are adjusting the cars individually, on at least a weekly basis allowing for all the variables you mention. We have been timing each car, making tiers, making more mods and more tiers. They are running so smoothly now I can hardly believe it. All thats required are: brake lights, new liveries, decals.. and there are still about fifteen more to rebuild. (lol). Hence, with the ever increasing price of C7005s I have been prompted to change chip. Four or five C7005s are away under repair. I have learned so much recently here I may / should be able to handle future smoke issues myself. ;) Dream on...

Future project: building up an INCARPro flashed fleet of something or others, now we (in inverted commas), have the technology.

:)
 
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