...Remapped FN3 vs FN2 direct comparison

16715 Views 114 Replies 24 Participants Last post by Relic, Mar 2, 2012

Relic

Discussion Starter · Feb 28, 2012 (Edited)

8

Was having a discussion with costel1 about the issues with diesel torque mountains and such when cornering.
To cut a long story short I was saying how the FN2 can take corners so well is down to the fact the torque curve is almost flat.
So you have total control of the power into and out of the corners with no sudden power surges to destroy the grip and spin the wheels.
[vtec point aside]

Anyway, one thing led to another and I decided to translate the FN2 engine dyno to an FN3 engine Dyno.
The gear ratios are not perfectly proportional between the two cars though and neither is the weight.
So both of these had to be taken into account.
Ive been ultra conservative with costel1s dyno and used the hub figures as I was unhappy with the transmission losses used.

The Methods.

CONVERT ENGINE RPM:
FN2 RPM / (FN2 1ST GEAR RATIO x FN2 FINAL DRIVE) x (FN3 1ST GEAR RATIO x FN3 FINAL DRIVE) = EQUIVALENT FN3 RPM
FN2 RPM / (FN2 2ND GEAR RATIO x FN2 FINAL DRIVE) x (FN3 2ND GEAR RATIO x FN3 FINAL DRIVE) = EQUIVALENT FN3 RPM
...and so on for each gear...

CONVERT ENGINE TORQUE:
FN2 TRQ x (FN2 1ST GEAR RATIO x FN2 FINAL DRIVE) / (FN3 1ST GEAR RATIO x FN3 FINAL DRIVE) = EQUIVALENT FN3 TRQ
FN2 TRQ x (FN2 2ND GEAR RATIO x FN2 FINAL DRIVE) / (FN3 2ND GEAR RATIO x FN3 FINAL DRIVE) = EQUIVALENT FN3 TRQ
...and so on for each gear...

BHP = RPM / 5252 * TORQUE

CORRECT FOR POWER TO WEIGHT:
(FN3 WEIGHT + DRIVER WEIGHT) /
(FN2 WEIGHT + DRIVER WEIGHT) = WEIGHT PENALTY
BHP = BHP x PENALTY
TORQUE = TORQUE x PENALTY

The Results.

Then its just a question of plotting the info on a graph for each gear.
This shows exactly how much power/torque is required at what rpm for an FN3 of given weight to perform identically to a FN2 of given weight.
Theres 6 of these as the gears are out of sync.
1st is lowest and 6th is the highest on the graphs.

I then overlayed my TDI dyno which has become labelled the VTEC remap..which you'll soon understand exactly why;
And also overlaid costel1s dyno whose car is a little lighter than mine without the glass roof.

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1 - 20 of 115 Posts

RobertUtley

· #2 · Feb 28, 2012

So thus a highly tuned Derv would be quicker straight line but not around corners?

Impressive work though relic so comprehensive you wonder why people know you as the civinfo god!

coste1l

· #3 · Feb 28, 2012

so i would need to make 230bhp to 4800 to keep the lead i had gained between 2300 and 3600 rpm?

Relic

Discussion Starter · #4 · Feb 28, 2012 (Edited)

Yes mate.

You gain a few lengths but the FN2 claws some back as your power is midrange and fn2 power is topend.
You could also lower your weight further instead.

My biggest problem is also the weight penalty.

RobertUtley

· #5 · Feb 28, 2012

Relic said:
Yes mate.

You gain a few lengths but the FN2 claws some back as your power is midrange and fn2 power is topend.
You could also lower your weight further instead.

My biggest problem is also the weight penalty.

So lets be serious on the roads where our power is mostly used keeping to speed limits the diesels seem the more attractive and cost effective option

Relic

Discussion Starter · #6 · Feb 28, 2012

RobertUtley said:
So thus a highly tuned Derv would be quicker straight line but not around corners?

Impressive work though relic so comprehensive you wonder why people know you as the civinfo god!

The derv will never be able to hold a corner at as high a speed as the FN2 due to inertia.
The heavier derv will simply slip off line much earlier with the same tyres/grip.
Again....weight penalty appears the main issue.
A flatter torque curve would be much more controllable in the derv when cornering too.

coste1l

· #7 · Feb 28, 2012

did you factor in my lightweight wheels mick?

Relic

Discussion Starter · #8 · Feb 28, 2012

coste1l said:
did you factor in my lightweight wheels mick?

Nope

what weight would you like me to use and I'll knock up another at that weight.

coste1l

· #9 · Feb 28, 2012

lol well i lost 3kg a corner but the whole unsprung thing is a bit of a :worms:

Trevor7979

· #10 · Feb 28, 2012

Lee, your traction mid corner due to the torque is a massive help to grip levels.
The exit speeds might even be a touch higher!!!

Relic

Discussion Starter · #11 · Feb 28, 2012

RobertUtley said:
So lets be serious on the roads where our power is mostly used keeping to speed limits the diesels seem the more attractive and cost effective option

Depends if you want handling/noise or MPG.
Significantly reducing the weight on the FN3....Id say FN3 is a better option as the power is there, the mpg is there and the handling will be there.
Both are great cars in their own way and its a personal choice IMHO.

1. You'll never be able to get the weight down as much as you can with the FN2.
2. Tuning options are on the shelf for the FN2.
3. I think most would agree the soundtrack is better in the FN2.

Relic

Discussion Starter · #12 · Feb 28, 2012

3

coste1l said:
lol well i lost 3kg a corner but the whole unsprung thing is a bit of a :worms:

If you got your weight down to the same as the FN2...

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RobertUtley

· #13 · Feb 28, 2012

Relic said:
Depends if you want handling/noise or MPG.
Significantly reducing the weight on the FN3....Id say FN3 is a better option as the power is there, the mpg is there and the handling will be there.
Both are great cars in their own way and its a personal choice IMHO.

1. You'll never be able to get the weight down as much as you can with the FN2.
2. Tuning options are on the shelf for the FN2.
3. I think most would agree the soundtrack is better in the FN2.

I agree about the sound track i had my first time in an fn2 courtesy of Farboss and the teaming of the RSK and the exhaust (cant remember what) was very loud but the noise was unbelievable in vtech.

I am glad i didnt get a FN3 or watching you and Coste1l i would of been in the workhouse or in prison for non payment of debts due to the mods!

coste1l

· #14 · Feb 28, 2012

time for the angle grinder!!

Relic

Discussion Starter · #15 · Feb 28, 2012

:facepalm: :worms:

regan1985

· #16 · Feb 28, 2012

coste1l said:
time for the angle grinder!!

single seater FTW

thats about 30kg maybe more, the type r seats are even heavier

Fr0d

· #17 · Feb 28, 2012

Relic said:
The derv will never be able to hold a corner at as high a speed as the FN2 due to inertia.
The heavier derv will simply slip off line much earlier with the same tyres/grip.
Again....weight penalty appears the main issue.
A flatter torque curve would be much more controllable in the derv when cornering too.

I agree, and can tell you the torque steer and understeer of a tuned 2.2 on winter tyres, when trying to accelerate, round a very mild bend (and a few straights) is "interesting" sometimes.

Lunar Tick

· #18 · Feb 28, 2012

Good post and interesting read! And perhaps it underestimates the diesel's performance vs the FN2 as the FN2 weight is 1345kg, so less of a weight difference.

summ0004

· #19 · Feb 28, 2012

Interesting and accurate comparison, but it is comparing a tuned diesel to a stock CTR.

How many people keep their CTR stock these days?

Would be nice to see a comparison with the chipped diesel against a flashprod CTR that is otherwise stock. This would then give a nice comparison with both cars mildly tuned.

delta0

· #20 · Feb 28, 2012

A none stock CTR comparison would be interesting. The diesel life expectancy will really suffer from tuning, worth considering.

I'm looking forward to the new CTR as that will have a turbo. VTEC and turbo awesome!

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