Ask Rod... the REAL part of a top speed run is the HOLDING the power in 4th and 5th gear whilst putting on the big speed. Not the 1st and 2nd gear acceleration stuff mate. Pretty sure Mark and Rod don't even bother launching or giving it the full beans off the line on a topspeed run?

I know that starting from 0mph at bottom of the straight at Brunters or hammering around the bend at full speed has NO affect on Topspeed on Martins car.

 

I know about the standing start and hammering round the bend makes no difference, im just trying to say if your engine surges and ok especially above 5k then your acceleration towards your top speed must suffer. and you are correct Mark and Rod dont launch the car when going for top speed

 

It all depends on your gearing and how well your engine revs. If you have an engine that has surge at 5k but only revs to 7k and your ratios are really wide then it would be an issue as every time you change gear you would be back in surge zone. Lee on the other hand with solid lifters can rev a little harder and on a high speed run he would never see surge and it would not be an issue.

 

But you did... alot...

 

Rich, stop talking nonsense, do you know of ANY yb that surges OVER 5K?

Behave!

LOL


Porkies car goes like fuck and the surge only effects it when you are NOT on it, like he says, and pulling away in first the surge under 5K wont happen as the turbo wont make enough boost soon enough as it has a spool time that means in such a low gear its already past 5K by the time the turbo is really spooled anyway, even more so if he launches it hard and its already doing a few K rpm when pulling away and hooked up properly.

 

ok then say 2 cars have the 'exact' same spec say 600 bhp is it a hit or a miss if 1 does 175mph all day long will the other do the same?? or is that a stupid question

 

How many BHP does each one have after being "on it" for 20 seconds and the charge temps have gone through the roof etc?

And then you have gearing and the shape of the power/torque curve to contend with, as 600bhp isnt tellign the whole story.

 

ok so say the graphs where almost identical with the torque the same & charge temps, is it a hit or miss in wich gets the all important top speed or would they be the same there also?

 

Well assuming the same gearing, then they are going to perform the same if the output is the same, more or less.

 

hmmmm very interesting

 

I still don't think surge will have any seriously detrimental affect on acceleration.

 

It will if you suffer it while you are trying to accelerate, especially as the side effects of surge include increased intake temps

 

yeah, loadsa cars surge above 5k

seriously rich, i know this is a bit late, but how often you think a cossie with traction is gonna be below 5k when giving it some on the dragstrip, or franky, anywhere?

 

aint read all the thread but having lots of bhp means nothing u can have a
400 bhp car it left by 340 bhp car u want lots of torque thats wot makes a car pull through the gears!!

 

Thats just nonsense.

Torque @ the wheels is what counts, and that is a product of BHP not Torque @ flywheel as it takes into account gearing.

A 400bhp 300lbft car is quicker than a 300bhp 400lbft car if both are geared correctly and same weight etc.

 

The bottom line is : If your turbo's correctly spec'd to your engine, and you avoid surge.......Then you'll have a better "Drivers Car".

 

Good read lol

What about that boy "nutters" 3 door , think its his 3 door that does serious times ! ? oops might be a 500 not sure

 

Steve Scott in the WRC car, one of the quickest cossies round a track on this board.

My money would be on him round Donnington against anybody, period.


Closesly followed by Stuart Whyte, Gallagher and Doherty.(scottish boys love it )

Oh and Martoon for good measure in his weapon of mass destruction.



Its all about round a race track for me rather than a straight line blast or Poddington.




Have a chat with Butch on this one on his stock engine and T34..lol

 

You would be wrong to put your money on him

But if your up for a bet my money goes on Gareth lloyd... NO cossie has gone round Donington as fast as him!!

 

If you say so and do read as I did say "one of the quickest" but to be fair, Gareth was the other name, who I have just been racking my brains to add to the list.

Superb car and driver and I know he and Steve have a lot of respect for eachother

 

i dont know of any yb that surges over 5k, i was just saying if it did then it would be relevant to a hindered top speed run

 

I think that one with a block made of marshmallows would be a bad idea too, but I dont know of any of them either.

 

yes chip

 

right ok,this has got very interesting but can someone explain what surge is and how it affects the car?

 

Stu had done a good post on this, but the search on here and me dont get on, lol


Essentially though its when the turbo pushes more air through than the engine can swallow so it ends up coming back through the turbo again, which makes he "chatter" noise like you have backed off the throttle.

 

what while on boost? is it ok for it to do it when you let off/change gear then?

 

Yes mate, while on boost.
As for if its ok whne you change gear, it depends on the turbo, which is why some HAVE tohave a dumpvalve.


Basically turbos have a "surge line" on the compressor map, if you try and make too much boost at too little flow you cross this line.

One way to guarentee you cross the line is to shut the throttle when the turbo is spinning hard.

 

my t34 does it on let off but i removed the standard dumpvalve. i take it the gt range need a dumpvalve then?does it have to be atmosphere or can you use re-circulating?

 

Yes mate GT turbos expire quickly without a DV, either tyre is potentially ok, but if running big boost a recirc wont flow enough, in fact people often need 2 DV's on the GT35 and above.

 

gotta say tho, i know people running 1.5bar on GT30 sized GT turbos and no DV with no probs

 

i hate dumpvalves,if i do eventually ever manage to get a gt range one i will have to try and go re-circulating if poss.
may just be me but i think they sound a bit tacky.

 

Surge is surprisingly loud!

Remember hearing it at Bedford when this cossie was coming past the pitlane, and it sounded awful!