Type 9 Top Speed?

[garethbowers]

Hi all finally got round to taking her out for a spin. I have a 2b with a e reg sierra type 9 coupled with a 168bhp at the wheels vauxhall xe engine.

 

God she pulls like a train through 1st 2nd 3rd and a chunk of 4th. The thing is she seems to run out of puff in 5th with my lump at approx 4-5k ( i think). Basically doesnt seem to pull amymore. My speedo isnt working yet and im now not sure if my rev counter is correct (however i feel it is).

 

What i would like to know is what is the top speed likely to be and is there anything i can do to lengthen 5th gear? I get the feeling im doing about 65-70 but im not sure.

 

Thanks for the input peeps

 

Gareth

[agent_zed]

Hi, if you have the maths skills its possible to work out your theoretical max speed. When your engine is doing its max confortable rpm it can only turn the wheels at the speed of the gearing, its not possible to go faster as your engine would have to go faster if you see what i mean. So if you know your gear ratio for 5th, the gearing of your diff and the diameter of the wheels its possible to work it out.

 

You probably won't get that speed as aerodynamics and rolling resistance will hold you back.

 

Ive heard it said that the caterham has a drag co-efficent rating of 0.7 which is pretty close to being a brick (CO of 1) a sierra is significantly more slippery at about 0.34 from memory. Which is why you'll never get a huge top speed in a 7. But who cares really as they are built for the curves

 

If you want to change the gearing you can either fit wheels with a larger circumference or a diff with a different ratio.

 

hth

[Peter Bell]

Gareth send me a pm with your email address and I will send an excel sheet for speed/gearing.

I tried to Pm you but got the message you can't receive any more messages!

[Snapperpaul]

Top speed will be achieved in 4th as 5th is an overdrive.

If you can't max out the revs in 4th with a Vauxhall lump the go for a 3.9 diff.

Look for the gear speed calculator, there ate a few on the web, you can look at what speed you can get in each gear and dial in diff ratios and tyre sizes

Edited August 2, 2010 by Snapperpaul

[Guest Ian Marr]

Top speed will be achieved in 4th as 5th is an overdrive.

 

As an armchair mechanic my curiosity got me on this one. Why would a car not go faster in overdrive than in 4th?

 

Not looking to question the logic, just understand it.

[Guest peter2b2002]

sounds like your dif ratio is wrong, my 2ltr efi pinto can do more the 110 in 5th before it runs out of puff(on a race track)

peter2b

[megadodo]

As an armchair mechanic my curiosity got me on this one. Why would a car not go faster in overdrive than in 4th?

 

Not looking to question the logic, just understand it.

 

4th gear in a type 9 is 1:1 and 5th is overdrive and is used to lower the engine rpm to improve fuel economy at motorway speeds. When matched with the correct diff ratio it could be faster in 5th than 4th but in some setups the engine hasn't got the torque/power to overcome wind resistance in 5th, but in 4th it can hit max revs which happens to be a faster speed than it can pull in 5th. Try your car on a hill and you have to change down sometimes to keep going as the engine can't spin fast enough to deliver its power! I hope that hasn't confused you more?

[steve in stockport]

Gear speed calculater HERE

 

I've had my red top up to 5.5k in top, and it still wanted to keep going, but I was running out of road and bottle!

 

Steve

[speedtripledan]

Strange my 124bhp at the wheels pinto with 3.62 diff and type 9 will pull 116mph in 5th in a 2B (GPS on a track ) The 3.92 was just serouisly undergeared for mine the vaux engine with that sort of output should easy rev out in 5th

 

Do you know what diff you have got ? might be a 3.14

[garethbowers]

hey all thanks for the replies, i can rev easily in 4th to 6.5k 5th was aabout the same. Ill have to get my speedo working and see how fast im goin. It didnt seem that fast to be honest. The e is 168 at the wheels and 370 lb ft

 

Ill have to make sure the rev counter is reading correct.

[Snapperpaul]

I am currently running a standard Pinto while my super duper pinto is being completed( by me) it will rev more in 4th than 5th.

With the 130bhp engine in it would max out in 4th but not 5th but would still pull similar top speed red line was 7000rpm

Next engine, well we will see but hoping for over 150 bhp with a red line of 8000, there is no way on Gods earth I will see the revs max out in 5th as that would be over 150 mph

[Snapperpaul]

370 ftlbs , turbo or super charger?

[garethbowers]

N/A mate goes like a trooper. Ill know more once ive sorted the speedo. Unless im stuck in 3rd lol... Really does shift in the 1st 3 gears tho. How would i know what diff i had matey? Here's my dyno graph.

 

Gareth

Edited August 3, 2010 by garethbowers

[speedtripledan]

if you lucky there will be a metal tag on the casing which tells, you might need a clean to read if not it will be a case of counting revolutions etc

[Guest pwlcarz]

If you want to check your speed (as your Speedo's not working) why don't you beg/borrow a Sat Nav?

Most will show your average speed over about 2 - 3 hundred yards. I find mine is more accurate than the speedo which tends to over read.

 

Just a thought.