Gear ratios changed?

di1in · 25th August 2010, 22:40

It's been nagging at the back of my head for some time, hope someone could explain it to me.

After I installed a free flow from Raj,apart from all the positives i noticed one negative point about the whole thing. It was as if my gear ratios had changed. Before the FFE, i reached almost 105km/h redlining at second gear. But now it peaks at around 97. Likewise 5th gear @ 2000rpm gives me 70 while i used to get 80km/h before.
What could be the reason? Thanks in advance guys.

P.S: Googling about this led me to a thread where someone had a similar problem when he used a shorter length air intake tube. But when he stated his problem everyone ridiculed him stating that gear ratios had no relation to airfilters and such. Hence the title.

condor · 25th August 2010, 23:31

@di1in, if you got a FFE, how can gear ratios be changed ? Gear ratios are about the gears inside the gear box. You have got yourself a different exhaust, not a new gear box / new gears inside the g/b.

nitrous · 25th August 2010, 23:34

Did you change tyres?

di1in · 25th August 2010, 23:50

Quote:

Originally Posted by condor

@di1in, if you got a FFE, how can gear ratios be changed ? Gear ratios are about the gears inside the gear box. You have got yourself a different exhaust, not a new gear box / new gears inside the g/b.

uhm, thats my question.. as to how those speedo readings changed. I'd though the only way was to see a change was through gear ratios until nitrous reminded me about the tires.

Quote:

Originally Posted by nitrous

Did you change tyres?

Yea, but i'd upsized a couple of months prior to the ffe installation.

Bot now that i think of it, i hadnt driven the car much until after the ffe so maybe thats why i noticed it just then.

Thanks nitrous! You the mann!!

nitrous · 25th August 2010, 23:56

Can you post your old and current tyre sizes?

dhanushs · 26th August 2010, 00:05

I think if the clutch is not transmitting the entire power, then this fluctuation in speed could occur. but, installing an FFE should not affect clutch performance, should it?.

Experts, please comment.

PAVAN KADAM · 26th August 2010, 00:07

Its probably wrong FFE set-up.

I too had the same issue with Raj's FFE on my M-800.

My top speed changed from 125 kmph to 120 kmph, Car struggled to breathe after the top speed, i too felt the way the gear box handled was funny, but got it lightly altered with someone else later.

Now my car easily touches 135+ kmph with Headers and stock muffler.

With Headers, my initial pick-up increases by leaps and bounds.

I have also altered a M-800 gearbox with shorter gear ratios, but with that gearbox, the car just flies, so will use it when i feel i need to refresh

If you are altering the gear ratios, make sure, you also get a matching gear shifters, else, you could be stuck driving in 2nd gear or in Reverse.

di1in · 26th August 2010, 00:13

Quote:

Originally Posted by nitrous

Can you post your old and current tyre sizes?

Old: 170/70/R13
New: 195/55/R15

It's probably the tire size difference - there's around 3.5% difference.

I've updated the post below.

di1in · 26th August 2010, 00:20

Quote:

Originally Posted by dhanushs

I think if the clutch is not transmitting the entire power, then this fluctuation in speed could occur. but, installing an FFE should not affect clutch performance, should it?

Considering the way people (like me) drive after gettin hold of a ffe, there won't be much left of the clutch

. its the exhaust note that my right foot is addicted too..

Quote:

Originally Posted by PAVAN KADAM

Its probably wrong FFE set-up.

I too had the same issue with Raj's FFE on my M-800.

My top speed changed from 125 kmph to 120 kmph, Car struggled to breathe after the top speed, i too felt the way the gear box handled was funny, but got it lightly altered with someone else later.

What kind of alterations?

Is that muck buildup near the top of the headers a sign of somethin bad?

SirAlec · 26th August 2010, 01:01

Quote:

Originally Posted by di1in

Old: 170/70/R13
New: 195/55/R15

It's probably the tire size difference - there's around 3.5% difference.

I've updated the post below.

Thats a very serious upsize.

Download this, unrar it and use it calculate the difference. (you can open this in IE explorer)

tyre size calculator.rar

dhanushs · 26th August 2010, 02:52

The tyre change accounts to only about 3-4% change in speed. This still does not justify the change in speedo reading as its much higher than this. You should look for other reasons, I guess.

di1in · 26th August 2010, 10:55

Quote:

Originally Posted by SirAlec

Thats a very serious upsize.

Download this, unrar it and use it calculate the difference. (you can open this in IE explorer)

I did calculate eariler, and it gives around 3.5% difference.

Quote:

Originally Posted by dhanushs

The tyre change accounts to only about 3-4% change in speed. This still does not justify the change in speedo reading as its much higher than this. You should look for other reasons, I guess.

You're right, my speedo shows a difference of about 9%. I did a few runs today morning, and during the initial drives i got about 75kmh @ 2000rps @ 5th gear. After a couple runs it came back to 70.

Do you think the colder engine bay temp had something to do with this?

Or like PAVAN KADAM said, would i have a faulty installation? I've attached a pic a few posts back where there is muck stuck near where the headers and gaskets meet the engine block.

And finally, is there a way for me to check whether my clutch plates have worn off by DIY? My mech is outta station due to Onam.

dhanushs · 26th August 2010, 12:34

Different speedo readings during the same run leads me to believe that you've got a faulty tacho/speedo. Please check if these are OK.

Difference in engine bay temperatures may sometimes show a slight difference in vehicle performance, but, then showing different speedo readings for same rpm - I dont think so.

Again, a worn out clutch can have the above said effects. The best symptom of a worn out clutch is that, on some extreme situations (like trying for a wheel spin on a tarmac with loads of grip) you sometimes feel your car is not traveling enough for the amount of pedal, ie, the engine would simply rev without transferring the torque to the gearbox/wheels. Also, there will be a noticeable drop in FE. Please check it out. - Experts please add to this.

pkumar · 26th August 2010, 16:25

The way i calculate, its 8.7% difference between 195/55/15 and 170/70/13.
Please check your calculation.

di1in · 26th August 2010, 18:22

Quote:

Originally Posted by pkumar

The way i calculate, its 8.7% difference between 195/55/15 and 170/70/13.
Please check your calculation.

I calculated between 2 different calculators and it gives me 3.54% exactly between 195/55/15 and 175/70/13.

25th August 2010, 22:40	#1
di1in BHPian Join Date: Jan 2009 Location: Thrissur Posts: 511 Thanked: 285 Times View My Garage	Gear ratios changed? It's been nagging at the back of my head for some time, hope someone could explain it to me. After I installed a free flow from Raj,apart from all the positives i noticed one negative point about the whole thing. It was as if my gear ratios had changed. Before the FFE, i reached almost 105km/h redlining at second gear. But now it peaks at around 97. Likewise 5th gear @ 2000rpm gives me 70 while i used to get 80km/h before. What could be the reason? Thanks in advance guys. P.S: Googling about this led me to a thread where someone had a similar problem when he used a shorter length air intake tube. But when he stated his problem everyone ridiculed him stating that gear ratios had no relation to airfilters and such. Hence the title. Last edited by di1in : 25th August 2010 at 22:43.
	() Thanks

25th August 2010, 23:31	#2
condor Distinguished - BHPian Join Date: Jun 2006 Location: Speed-brkr City Posts: 15,864 Thanked: 16,008 Times View My Garage	@di1in, if you got a FFE, how can gear ratios be changed ? Gear ratios are about the gears inside the gear box. You have got yourself a different exhaust, not a new gear box / new gears inside the g/b.
	() Thanks

25th August 2010, 23:34	#3
nitrous Senior - BHPian Join Date: May 2004 Location: UAE/Lon/Madras Posts: 6,965 Thanked: 325 Times View My Garage	Did you change tyres?
	() Thanks

25th August 2010, 23:56	#5
nitrous Senior - BHPian Join Date: May 2004 Location: UAE/Lon/Madras Posts: 6,965 Thanked: 325 Times View My Garage	Can you post your old and current tyre sizes?
	() Thanks

26th August 2010, 00:05	#6
dhanushs Distinguished - BHPian Join Date: Oct 2009 Location: Chennai Posts: 4,280 Thanked: 10,171 Times	I think if the clutch is not transmitting the entire power, then this fluctuation in speed could occur. but, installing an FFE should not affect clutch performance, should it?. Experts, please comment.
	() Thanks

26th August 2010, 00:07	#7
PAVAN KADAM BANNED Join Date: Jan 2007 Location: NAMMA BENGALURU Posts: 5,602 Thanked: 2,549 Times	Its probably wrong FFE set-up. I too had the same issue with Raj's FFE on my M-800. My top speed changed from 125 kmph to 120 kmph, Car struggled to breathe after the top speed, i too felt the way the gear box handled was funny, but got it lightly altered with someone else later. Now my car easily touches 135+ kmph with Headers and stock muffler. With Headers, my initial pick-up increases by leaps and bounds. I have also altered a M-800 gearbox with shorter gear ratios, but with that gearbox, the car just flies, so will use it when i feel i need to refresh If you are altering the gear ratios, make sure, you also get a matching gear shifters, else, you could be stuck driving in 2nd gear or in Reverse.
	() Thanks

26th August 2010, 02:52	#11
dhanushs Distinguished - BHPian Join Date: Oct 2009 Location: Chennai Posts: 4,280 Thanked: 10,171 Times	The tyre change accounts to only about 3-4% change in speed. This still does not justify the change in speedo reading as its much higher than this. You should look for other reasons, I guess.
	() Thanks

26th August 2010, 12:34	#13
dhanushs Distinguished - BHPian Join Date: Oct 2009 Location: Chennai Posts: 4,280 Thanked: 10,171 Times	Different speedo readings during the same run leads me to believe that you've got a faulty tacho/speedo. Please check if these are OK. Difference in engine bay temperatures may sometimes show a slight difference in vehicle performance, but, then showing different speedo readings for same rpm - I dont think so. Again, a worn out clutch can have the above said effects. The best symptom of a worn out clutch is that, on some extreme situations (like trying for a wheel spin on a tarmac with loads of grip) you sometimes feel your car is not traveling enough for the amount of pedal, ie, the engine would simply rev without transferring the torque to the gearbox/wheels. Also, there will be a noticeable drop in FE. Please check it out. - Experts please add to this.
	() Thanks

26th August 2010, 16:25	#14
pkumar BHPian Join Date: Feb 2008 Location: bangalore Posts: 181 Thanked: 6 Times	The way i calculate, its 8.7% difference between 195/55/15 and 170/70/13. Please check your calculation.
	() Thanks