got a question, for Jake Raby Options

[bd1308]

you said in a previous post that one should not go below 3500RPM in 5th gear, as the airflow is not sufficient enough for proper cooling.

i have some problems with this....

1) in my car, at 70mph, I am around 3200RPM in 5th...sometimes i am even running 3000RPM and occasionally run even 2800RPM for short periods of time. Are you suggesting that I should not shift into 5th gear at all?

2)I have also heard that the type 4 cooling fan efficiency goes down after around 4000RPM....it was mentioned by someone on this board, but the user name escapes me. Is this true?

I tried running 75 in 4th gear and I was running more than 4000RPM.....

I think i am missing something....

[914forme]

QUOTE (lapuwali @ Aug 3 2005, 06:21 PM)

so your speedo reads high by about 7%.  70mph indicated is 65mph actual, assuming the speedo was accurate to begin with (not bloody likely).

This is why I run a know run with a GPS, I find my true speed or pretty darn close, and avoid finding it via a radar gun.

My 914 runs way shorter tires than stock, My Jetta went plus one in wheel size and keep the same aspect ratio so I went way up. That was drop the revs on the jetta and get it closer to 2000 RPM and 70 MPH, its a TDI, it likes low revs (IMG:http://www.914world.com/bbs2/html/emoticons/smile.gif)

Grab a GPS and find a measured mile and see what you get.

This is the exact reason Porsche used a lower 5th in the -6s was to keep the revs up and help the fan do its job. Works for our -4s also.

Due to lovely mandates and our sue them attitude society your speeedo will read low even with everything including the planets being aliened. Just the way it is, the odo's are usually a little more accurate. But I would not use them to measure a true mile or kilometer with.