Tuning potential

[Craggy]

can someone explain why different engines react completely different to mods? take say for instance a certain 1.6 has the following spec and runs 14s 1/4 mile:-

stripped interior
Piper 285 cams
4.5 bar fuel pressure regulator
Superchip
stainless cat-less exhaust


yet some motors have sh*tloads done and seem to get nowhere. is it all down to flow, and ooeeerrr perfecr head(what we all desire) in an engine sense of course

craggy

 

[paddymph]

weight of a certain 1.6 might have summat to do with it?

 

[Craggy]

nah, barely lighter than a valver, bout 35-40 kgs

 

[Ben H]

Its odd isnt it!

 

[paddymph]

errr, luck? dunno mate?

 

[Craggy]

lol, leasat ur trying paddy mate, must be something to do with engines designt in the first place, cos you can only do so much to one i suppose without making summat from scratch

 

[paddymph]

yeah exactly.

dunno, ask BenR or Slarty, oh no he got fecked off.......

 

[Mike Wright]

BHP = Torque (ft/lbs) x rpm/5252. This basic equation is the cornerstone of all engine design and development work. Two main methods of measuring power are used in the automotive industry - (1) measurement at the crankshaft of the engine or (2) measurement at the driving wheels


Average real transmission losses are about 10% of the flywheel power plus 10bhp for FWD cars and 12% plus 10bhp for RWD cars. This equates to about 15% to 17% for cars of "average" power output.

So in summary there are many factors which affect performance etc including ancillaries, conditions and set up. The answer to your question in my opinion is a complex one! Christ how boring am I!

 

[adiclio16v]

must be down to engine design, maybe 1600 16v motors as fitted to vtss are a really good engine and then are detuned in accordance with the rules govening emissions and all that

wheras some engines are a bit sh!t and struggle to make decent power so tuning cannot be took much further

i heard vtrs are really restricted from the factory to keep the performance gap between that an the vts quite big and the vtr insurance low

 

[Craggy]

lol thankyou mike, never thought about trans loss, those paper, i mean titanium citroen drive shafts and plastic gearbox probably have 2% trans loss. qestion answered

 

[BenR]

Quote: Originally posted by Mike Wright on 17 March 2003

BHP = Torque (ft/lbs) x rpm/5252. This basic equation is the cornerstone of all engine design and development work. Two main methods of measuring power are used in the automotive industry - (1) measurement at the crankshaft of the engine or (2) measurement at the driving wheels


Average real transmission losses are about 10% of the flywheel power plus 10bhp for FWD cars and 12% plus 10bhp for RWD cars. This equates to about 15% to 17% for cars of "average" power output.

So in summary there are many factors which affect performance etc including ancillaries, conditions and set up. The answer to your question in my opinion is a complex one! Christ how boring am I!

http://www.pumaracing.co.ukwww.pumaracing.co.uk

LOL.....sorry.....

Anyway, craggy.

This is an odd thing isnt it.

Anyway, in terms of pure drag racing, torque is qhat does it, if you seach it up and compare the torque/ltr and torque/ton ratio as opposed to bhp/ltr or bhp/ton ratio and see what happens?

The 1.6 in std trim makes about 120 right, and the 1.8 valver makes 137bhp. Not a huge difference and in real life, barely worth noting. for you to convincingly beat a similar powered and weight car, another 30-50bhp is what you need.

The valver has a very very good head design, but its larger ports mean low velocities at low engine speeds. This low velocity means low inertia and poor cylinder filling until you reach any decent rpm. The pug/citroen engine has a worse flowing head, but more than enough for the 120 its making. This means cams which arent so whacky and have little overlap and less duration. At low rpm, it has a stronger signal (ref to teh diff in cylinder capacities and volume work @ the same rpm) helps to keep torque on a flatter curve.

Its hard to explain, but lets just sayt eh F7 head flows TOO well for its current application. It can do with alot more.

 

[Mike Wright]

Spot on Ben but I didnt say it was my words mate. If it was I would add some humour to it! (Just tried to help) Thats why I put the wink in there!

 

[BenR]

good example is my MK1 XR2.....the in std trim it makes 86bhp, with its n20 on (a modest 40bhp jet, but they never equal the bhp rating) it a match for Aarons valver, which we all know is surprisingly fast and faster than a willy for some off reason.

With the std head off, i can tell you its AWFUL in std trim, but the engine has potential for a good 180bhp with lots of work.

 

[BenR]

NO worries mike, all i know is hes picky with his copyrights and i see alot of people wuotting his words....lol......hell, i read it too, its a good site.

 

[Mike Wright]

 

[Craggy]

cheers ben, glad we cleared that one up some more. must say im desperate for throttle bodies for my williams and some mad high rpm but those large ports are crap for throt bods apparently hence the need for megane head

 

[BenR]

nah, the ports are fine.....its a great head.

They are crap for any lmited TB and inlet manifold, and the std system just about makes it.

I would deffo NOT revert to a megane head. Sticking on throttle bodies will make the car scream, im in the process of putting together a kit on mine.

 

[Craggy]

was meaning to ask you that! glad you remembered for me lol, cool, will sound awesome