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RPM at speed?
edspurrier - 28/10/08 at 07:39 PM

Took the Tiger (Avon, Zetec 2 litre, Type 9 and a Sierra diff of uncetain ratio) on motorway for first time. 5500 RPM at about 70mph. Is this normal? Expected quite a lot due to the aerodynamic efficiency of the Tiger but that;s a bit more than I expected

Thanks
Ed

TOO BADD - 28/10/08 at 07:44 PM

Were you stuck in 2nd gear ?

blakep82 - 28/10/08 at 07:46 PM

i'd have guessed nearer 3000 should be normal?
don't think aerodynamics should come into it, since there should be a direct relationship between engine speed an wheel speed in 5th gear

phoenix70 - 28/10/08 at 07:47 PM

Nope, not normal at all. Mine is doing about 3000 rpm in top at 70mph, thats on 14 inch rims with a 3.62 diff (I think)

blakep82 - 28/10/08 at 07:50 PM

might was to check the diff ratio? doesn't sound suitable

edspurrier - 28/10/08 at 07:53 PM

Might I suppose have been stuck in 3rd. MIght go for a quick check spin now.

Diff has both 3.6 and 3.9 written on it in marker pen, so not sure at all which it is!

Paul (Notts) - 28/10/08 at 07:54 PM

somethings not right....

Tacho reading

Speedo reading

Are you sure your in 5th gear

if correct then your diff must be around 6:1

Paul

TOO BADD - 28/10/08 at 07:54 PM

Or... check the tacho is set correctly if it is setable.

blakep82 - 28/10/08 at 07:59 PM

yeah, did it SOUND like it was at 5500?

tomblyth - 28/10/08 at 08:02 PM

are you sure its 5500 revs if your pick up off the coil pack there would be an extra spark as ford run wasted spark that is rev counter read 5500 but engine only reving to half that 2775 which is more like it!

edspurrier - 28/10/08 at 08:02 PM

Tacho runs off Weber ECU. Must confess mate was driving and I was following so not sure about the noise - will try it on SUnday I think. Too cold and wet out there now.

That said all seemed to work and responds well, 60mph today with no problem and not excessive noise, so suppose probably all OK actually.

[Edited on 28/10/08 by edspurrier]

Paul TigerB6 - 28/10/08 at 08:23 PM

quote:
Originally posted by edspurrier
Might I suppose have been stuck in 3rd. MIght go for a quick check spin now.

Diff has both 3.6 and 3.9 written on it in marker pen, so not sure at all which it is!


Its a fair bet you were!! I dont think there is a Sierra ratio available that would give you such a rubbish top speed!! I had a 4.1:1 in the Cortina axle of my old Super 6 Zetec and that was fine.

edspurrier - 28/10/08 at 08:31 PM

Thanks.

What diff ratio do people who've had the choice prefer for fast road / track use?

clairetoo - 28/10/08 at 08:39 PM

quote:
Originally posted by edspurrier

What diff ratio do people who've had the choice prefer for fast road / track use?

My fave is 4.1 - I used that with a tuned crossflow/type nine , and I have the same in with a V6 and Mx5 box .
The type 9 setup gave 4000 at 80 , very near to peak torque .

David Jenkins - 28/10/08 at 10:04 PM

Similar to Claire - I have a 3.89:1 diff from a 1300 Escort, which gives rpm around 3500 at 70mph in 5th (type 9).

[Edited on 28/10/08 by David Jenkins]

mat.price - 28/10/08 at 10:06 PM

i have a 3.92 diff with my pinto it's nice but i don't know what rev's im doing at 60/70 mph as i have not rpm meter but even that only sounds about 3 maybe 3500 at 70ish

jabbahutt - 29/10/08 at 07:53 AM

sorry to Hijack but I have the very problem Tom notes. My tacho is reading double the true revs.

The input is being taking off the coil, is there any easy way to correct this?

Cheers
Nigel

edspurrier - 4/11/08 at 02:29 PM

Does about 4400 at 70mph, which is I think a bit on the high side. So something's not quite right.