6000 rpm +
Turbo Mini Forums

turbo max power is aprox 6000 revs, having used 8000 n/a engine, ie, more top speed, how can you get turbo to rev more.more topspeed

you can get a turbo to rev...

but revs dont give you anything.... so why bother!!

Its all about the torque and engine produces :)

Alex

AlexF

alex if your in top gear every 1000rpm is 15mph, 4000rpm =60mph 6000mph is90mph 7000rpm=105mph, so mopre top speed

the mph per engine RPM depends on teh gear ratios. if you want more top speed you run a lower final drive :) and let the torque pull you through it.

eg my old 998 did 90mph at aprox 5500RPM, my 1380 with its gearbox and final drive will pull 90mph at ~4300RPM.

turbo 16v k-series 11.9@118.9 :)

Denis O'Brien.

Revs don't give you anything???

You mean generally, or in a std metro turbo engine?

Im right in thinking jon's revs to 7k?

Not sure what the power is like up there but guess its pretty good, felt it when he took me out in it!!

I mean revs don't give you anything on there own...they are fine if there is plenty of torque at the high rpms, but most engines don't.

With our turbos we don't need to rev them as we have so much mid range torque we can easily gear the car for silly top speeds (just use a 2.7:1)!

Alex

AlexF

Top speed is all about the balance of drag and BHP, when their forces match you can go no faster. Drag is mainly the aerodynamic coeficient of the car, but tyre friction and transmission losses add a small amount of drag too.

So if you can get to your rev limit in top gear before the car is creating to much drag then you could in theory change the final drive ratio and increase your top speed. Be carful though, it will make the car slower to accelerate and if you get the final drive ratio totally wrong could cause a lower top speed!

http://www.twin-turbo.co.uk
http://www.hillclimbandsprint.co.uk/default.asp

A man without a project is like a like a woman without a shopping list.

Fair enough, but power is achieved from cylinder filling or Bangs / minute!
Having a turbo and doing both gives fantastic results however!!!

Totally agree you'd achieve little on a stock turbocharger (on a 1275 before ben or wil jump in!!!) on a std engine however!

grr I just typed a huge post and then pressed post and it error'd on me

AlexF

Exactly. Get a turbo A-series to rev to 8000rpm and it would fly.

I'm not entirely sure how you would manage this, 8-port head maybe?

Me and my bro' do jike to jump in, sorry.

Back to Coventry Climax engines: I know one fitted to a Davrian,998(ish)cc Turbo charged 160 BHP max rpm 8500 12 second 1/4 mile times.

Wil

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

Torque is turning force.

BHP is simply power, which is the amount of work done in a set time.

You can not directly measure BHP, instead you measure torque and calculate it over a set time to get the power.

Torque * RPM
BHP = ----------------------
5252


So to say "Top speed is all about the balance of drag and BHP" isnt right. What you need is good torque at high speeds. You could do this by having a high reving engine, but that isnt the only way.

As I said before you can pick you gear ratios to give you the right match to your engines torque curve. This will give you the most from your engine.

Alex

AlexF

everyone is right, we're just saying it in a different way - so that's nice

Wil

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

sorry to labour the point, but it is all about BHP and not torque when you are talking about top speed... well in a sence. It is all about torque at the wheels which is not torque at the flywheel.

For example. 2 engines both producing the same power. One produces it at 8000rpm and the other at 6000rpm, set the gear ratios to give the same torque at the wheels (i.e gear one up and the other down) and in theory they will have the same top speed. Therefore it is nothing to do with engine torque and all to do with power....... I think.

http://www.twin-turbo.co.uk
http://www.hillclimbandsprint.co.uk/default.asp

A man without a project is like a like a woman without a shopping list.

sorry alex, just read your post properly and I seem to have just repeated what you said in a much more complex way.... ops

http://www.twin-turbo.co.uk
http://www.hillclimbandsprint.co.uk/default.asp

A man without a project is like a like a woman without a shopping list.

Yeah we are talking about the same point in terms of gears and matching the power :)

Torque at the fly and torque at the wheels is irrevelent really, you have to have a gearbox and you loose a certian amount, its just a fact. But what you want is torque at high rpms!!

If you want a high top end speed you need to make sure there is plently of torque high up in the rev range. This will give you a high BHP figure as there is lots of work being done in a short amount of time

Alex

AlexF

or, to put it another way,
Get a turbo A-series to rev to 8000rpm and it would fly

Sounds good to me! bit of a challenge i think!!

Might have to get a decent crank put in mine just in case i decide to make it rev well!! lol!

Hmm vtec style a-series!

most of the miglia guys rev there engines over 8k, using std metro rods and crank, just ballanced,

Team Racing

well what a can of worms we have opened here.

here is the hogsters point of view.

N/A engines which produce high hp fiquers do so because the cam head and carb set ups alow this to get the engine to rev but all N/A races and sprint car use silly high diffs to use these high reving torque and hp to move the car, most races which rev to 8k and above drive like a bag of s@it until about 6k then the sprint off.

but turbo engines will give the same if not a lot more torque and hp fiquers a LOT LOWER DOWN AS MUCH AS 4500RPM FOR MAX TORQUE, SO AS ITS THE TORQUE WHICH IS THE MOST USE TO PROPELL THE CAR THEN THATS WHAT YOU HAVE TO UTILISE.

SO IF YOUR CAR IS A BIG TORQUER THEN GEAR IT SO.

IE USE A 3.1 TO A 2.9 AND USE THE TORQUE AT HAND.

CANT UNDER STAND WHY WE NEED TO USE 3.4 AND ABOVE DIFFS FOR TURBO UNITS.

I CURRENTLY ARE USING A 2.9 IN THE HOG ALL BE IT SHE STILL IS N/A 1380 BANGING OUT 100BHP AT 5750RPM AT 103 FT LB TORQUE. BUT WNEN RUNNING THE TORQUE REALEY PUSHES THE CAR FORWARD.

ONE MAJOR FACTOR FOR THE MINI HOWEVER IS THAT ITS GOT THE AERODYNAMICS OF A BRICK. WHICH DOESNT HELP THINGS .

always looking for them bigger bunches of bannanas

I'm using a 3.44 diff, (on 10's) but I have an lsd, so I can't go any smaller, 5 speed dog box is the only option for a higher to speed for me

Team Racing

on old challenge cars, they used 7500 of the start line,only reason i brought the subject up is some of the small hill climbs sprint tracks your gearing is so inbetween, so if you could just hold on that extra 1000rpm wow

If you tune the engine as you would a naturally aspirated motor you can raise the maximum engine power speed. I.e. with cams and modified cylinder heads, etc.

I currently run a swiftune sw10 camshaft, which is 280 and 290 degrees duration, but with less overlap than say a Kent 286, which is more suited to the turbo.

My maximum engine power is at roughly 6900rpm. But like people say you loose the low down power. I find with my setup it is coming on cam at the same sort of time its is coming on boost. So I cant really say you lose much!

If you run a T3 or large turbo with a large turbine section (less restrictive) then you can run more overlap and hence more duration. Due to less manifold pressure and less reversion into the cylinders

If using a smaller turbo, then you can make a much more usable and drivable engine. But with less potential for hp

Turbo size wont let you run more over lap !

Alex

AlexF

If you run a small turbo, with a small turbine, it will spool up much sooner but as it has a smaller turbine will create higher exhaust manifold pressure than a less restrictive turbine.

If the manifold pressure (back pressure to you) is high then reversion of the exhaust gasses can occur. Hence not as great a volume of exhaust gas leaves the cylinder, hence less power.

This is why most turbo engines have little overlap, or should i say, less exhaust duration past the point of TDC.

If a larger less restrictive turbine is used, manifold backpressure is reduced, reducing of preventing reversion, thus allowing more duration of the exhaust cam. I.e. later closing, hence, more overlap.