When to regear?

[funindubai]

My tyres are 285 70 17. My transmission is manual and the effect is quite pronounced. I am ble to drive in the sand but have lost the torquey feel completely. Most of the US blogs with this tyre upgrade have gone for a 4.56 regear.

I looked at the urd option but this requires separate ecu and is quite pricey. Do you have any experience with this supercharger? Trd have launched a 2013 fj in the US with a supercharger. A little hope...

[Paul]

Hi guys

Well the primary question still stands: "When to re gear"

I am not saying do or don't..... there is just a lot to think about.

- It is a semi permanent expensive mod.
- It needs a good workshop with this type of experience to do the work.
- It changes the performance profile of the car.
- It may change your re sale target market. as the mod makes it more of a dedicated off roader that cant easily be remover, like bumpers, big wheels and lift kits.

The performance profile shift is the most critical, for me.

Every time you jump down one ratio, you move the speed in each gear a little slower for a given rpm.
This may sound simple. If you drop enough in the ratio, you will in effect moved on one gear. So 1st become like LR, 2nd becomes like 1st was, 3rd becomes like 2nd was, etc, etc.

You need to consider the speed you typically drive at for the various terrain conditions.

It is not something to just jump into..... considering many people get excellent performance with doing nothing.

So:

Is it needed?........... Only you know, probably not.
Do you want it?....... Yes, Yes, Yes.
Can you justify it?.... No :(

Regards
Paul

[caprihorse]

It's very interesting discussion here and Paul is giving a lot of light into this subject.

However, I would never touch on my car anything, where hundreds of engineers from R&D spent millions of bucks on design. And you think, that they are idiots? It sounds for me like you would like to rebuild a Tercel to be able to compete with GT-R in a race...
If you're not happy with your current car, buy another one, which better suites to your needs, but do not try to improve the things, which are working, you'll just make it worse...

But, anyway, hundreds of responses and advices will not be a value for all those who say:

Do you want it?....... Yes, Yes, Yes.

[Wasif Ahmed]

My tyres are 285 70 17. My transmission is manual and the effect is quite pronounced. I am ble to drive in the sand but have lost the torquey feel completely. Most of the US blogs with this tyre upgrade have gone for a 4.56 regear.

I looked at the urd option but this requires separate ecu and is quite pricey. Do you have any experience with this supercharger? Trd have launched a 2013 fj in the US with a supercharger. A little hope...

Sorry no hands on URD SC experience but have heard a lot of good things about it.

So yours is a manual, what I have heard is that the gear ratios on the new manual GB are not as well spaced as that of the earlier manual GB ....

So how is the power and driveability now with the re gear ?

[Magnum]

It's very interesting discussion here and Paul is giving a lot of light into this subject.

However, I would never touch on my car anything, where hundreds of engineers from R&D spent millions of bucks on design. And you think, that they are idiots? It sounds for me like you would like to rebuild a Tercel to be able to compete with GT-R in a race...
If you're not happy with your current car, buy another one, which better suites to your needs, but do not try to improve the things, which are working, you'll just make it worse...

But, anyway, hundreds of responses and advices will not be a value for all those who say:

Respecting the OP query, re-gearing comes always as a result of fitting bigger tires. It is in my opinion a corrective measure rather than a performance mod. What typically you would like to achieve by re-gearing is to restore the speed and performance of a vehicle with bigger tires to its stock state (as if, it is still running stock tires). Whether to do it or not is a personal call as Paul pointed out above.

In regards to the above quoted text by Caprihorse, I wouldn't omit the commercial factor involved in development of vehicles. In order for the R&D teams to spend that much of money in development, their companies have to make profits. Profits usually comes to a commercial vehicle manufacturer by catering for the majority of the consumers spectrum in the Market. A simple question could shed more light on the above; Why didn't Nissan use King or Radflo shocks and used Billestin? The answer would ultimately be "cost" related. They need to produce a vehicle that caters for the consumers needs and be in the same time within a wide range of spending. I mean at the end that their always is a "compromise". A more real example; if, my Xterra was over its current price tag, i would have never considered it in my car shopping list. I considered it as a good starting point and when I had the chance and the funds, I upgraded the suspension to what I thought the Xterra should come with. That's as well comes with a compromise that I personally accept happily.

Caprihorse, I note that you are not a big fan of modifications, but I note as well that you have a steel bumper on your Nissan. Isn't the bumper adding more weight to the nose of the car, and changing the weight distribution ratio the R&D spent millions to achieve? One more question, is it legal to fit such bumper on your vehicle?

Don't take my questions offensively, this is not my intention at all. Your answer to my question respecting the weight distribution ratio and the legality is not the point I'm trying to make here. What I'm trying to point out, basically, is you chose to do something; you applied your judgment and discretion, and decided to do it. That, basically, is the point I'm trying to make.

[caprihorse]

Respecting the OP query, re-gearing comes always as a result of fitting bigger tires. It is in my opinion a corrective measure rather than a performance mod. What typically you would like to achieve by re-gearing is to restore the speed and performance of a vehicle with bigger tires to its stock state (as if, it is still running stock tires). Whether to do it or not is a personal call as Paul pointed out above.

In regards to the above quoted text by Caprihorse, I wouldn't omit the commercial factor involved in development of vehicles. In order for the R&D teams to spend that much of money in development, their companies have to make profits. Profits usually comes to a commercial vehicle manufacturer by catering for the majority of the consumers spectrum in the Market. A simple question could shed more light on the above; Why didn't Nissan use King or Radflo shocks and used Billestin? The answer would ultimately be "cost" related. They need to produce a vehicle that caters for the consumers needs and be in the same time within a wide range of spending. I mean at the end that their always is a "compromise". A more real example; if, my Xterra was over its current price tag, i would have never considered it in my car shopping list. I considered it as a good starting point and when I had the chance and the funds, I upgraded the suspension to what I thought the Xterra should come with. That's as well comes with a compromise that I personally accept happily.

Caprihorse, I note that you are not a big fan of modifications, but I note as well that you have a steel bumper on your Nissan. Isn't the bumper adding more weight to the nose of the car, and changing the weight distribution ratio the R&D spent millions to achieve? One more question, is it legal to fit such bumper on your vehicle?

Don't take my questions offensively, this is not my intention at all. Your answer to my question respecting the weight distribution ratio and the legality is not the point I'm trying to make here. What I'm trying to point out, basically, is you chose to do something; you applied your judgment and discretion, and decided to do it. That, basically, is the point I'm trying to make.

Thank for the response.
Pls kindly explain your thoughts related re-gearing and bigger tyres. At first I'm questioning, why would somebody need bigger tyres? Just as a matter to impress his girlfriend? In a desert commonly used are 15" and 16" tyres, and bigger sizes are proved to be absolutely ineffective...

Nissan decided to use Bilstein maybe from commercial reasons or highly probably that they tested it and fined out that it is the best solution for Xterra off-road package. Xterra is produced in US and Bilstein in Germany. I don't see there any favoritism in that decision. I agree that there are many other OEM producers, who think that they can do better, supply more efficient equipment, if it fits to vehicle original spec, but still I disagree, if somebody is starting to change the physical construction of the vehicle, e.g. lifting. We had some cases with our drivers, who lifted their cars, made roll-over and never came back...

My metallic bumper is coming from my Newbie times, as I was frequently damaging it. One trip in a desert, claim for insurance, repair, and next week the same story... However my bumper weight is light, it's just 35 kg, it does not have any impact on my car stability, which is the most important for me, not to make rollover. Earlier RTA didn't care about metallic bumpers, so I was through without any problem. Now, I need to change it to plastic every year, just for renewal.

In majority of my so called 'negative' responses to the audience in regards of modifications, is, think twice before you do. Not just, I have money and I can do. For me personally the safety is the priority No.1. If I see wrongly modified vehicle in a desert, I'm very hesitant to allow it in our convoys.

[funindubai]

I am pleased to have started such a lively thread. And we have all learnt quite a bit from the discussion, especially thanks to Paul. My 5 fils worth on mods: as I said when I started the thread, we do them for looks mostly, but sometimes for function. I like the looks of bigger tyres on my car, I also happen to believe they offer greater capability in Some situations. I want to regear only to bring the ratios back to stock feel.
i concur with Magnum on the commercial storyline. Even a Porsche GT3 is modified by Porsche when it is brought to the track. There are commercial and practical considerations when designing a package. Some of us are more hardcore and for that we need to modify.

What I like about Capri's approach, is that it is safe in many ways: no risk of choosing wrong parts, resale issues, poor workmanship or quality of parts that can risk our safety in the sand or n the road. Unfortunately we are all not wired this way...

[Darshan]

@pwood:Completely agree. The 4.56 for the FJC is exactly what's required to bring it back to a stock feel. So agree with @ kennx that I dont want to be struggling to pass trucks in the right lane. Also I dont want the power, I'm just looking for more torque.


@ Al Shamsi: Yes I was hoping you could also share some experience and advise on supercharger install. I see you had the Unichip done. I wonder how the EGT on your car was as the Unichip tuning essentially takes out fuel and adds ignition to make the power. This indirectly has the effect of increasing EGT and also the temperature of your engine bottom end.

Will really appreciate your experiences, thank you.

Thank you funindubai for starting a refreshing thread. I am genuinely surprised at the number of new members who are techies. I haven't had the time to go through the entire thread (Will do so when I get the time)

For one, I know that none of the unichip owners have measured the EGT themselves so far. I have been in touch with a very popular US based tuner company directly for the last 6 months and I have been learning to tune. I have started right from how hydro carbon atoms hold hands and have been slowly moving upwards (missed some chemistry classes in school ;) )

That background was provided to you as a disclaimer so that you know that I am still a learner.

As you rightly said the process of tuning involves (in most modern cars) advancing the ignition and leaning the fuel a bit to bring it to lambda1. Now this is easier said than done. Because there are other dynamics to this. Most modern cars like your FJ works on an idle map, closed loop map and an open loop map.

It is the open loop map at fullload/full throttle that is usually tuned (that should answer the bottom end temp question if you really understand enough to ask that question) . Different methods can be employed to kick your car into open loop earlier and there is other trillion aspects to that which is out side the scope of your question.

Abt the EGT part, Your concern is valid, if you were tuning a very old car. In short, In the FJ when the temperature starts to rise high, the fuel burns before the ignition point there by causing knocking. Most tuners back off the ignition timing after several tests. Now even if the temperature rises uncontrollable due to some reason, the ecu combats it by retarding the timing automatically and raises it back after a bit of a cool down period. (Knock sensor magic)

Having said all this, what I see the usual local tuners do is to download a tested map for your vehicle (more aggressive one than what the unit came with) have the vehicle on a dyno for 30 mins and viola!!! done! If you go back with a knocking issue, he retards it a wee bit and TA DA!! off you go!!

My Advice to you: If you really have the experience of so many years offroading then, By all means go for the unichip and have it tuned. You wont regret it. As of now, the supercharger for our models is not out and the dream still evades me. Not that I need the supercharger, It is because I want one!

Our model of FJ is similar yet different to the 2010 model, the 2009 and prior models. The info that you find on fj forums regarding regearing are usually for older models and more specifically for performance at rock crawling and trail riding. Be careful for what you sign up to and since you have, let us know the feed back so that we can learn from your experience.

For ex: My FJ (2011) used to do about 75KM on first gear and now it has dropped to 62Km max speed after lowering the rim size by one inch. While at the same time, the 2010 model with the same engine specs as ours which comes stock 16 inchers run up to 75 effortlessly on first gear. There is no documentation anywhere about a difference in gearing between a 2010 and 2011. So be cautious. Some things are better if we leave it alone.

But then if you are anything like me ---Then-- Go mess with it, get down and dirty, Don't let go till you get it right, come back--- help others with your experience and first hand knowledge-- Relax with some beverages with the satisfaction that you learnt from your mistakes, got it right and then helped others!

Xkennx/Pwood/Funindubai: Looking forward to meet you guys some day (I know pwood already) Do keep the forum live with such good stuff!!

Have a lot more to write, but backing off coz I don't want people to fall asleep reading what I wrote :D

[Darshan]

By the way Moderators, Is this topic in the right section?

[Magnum]

Thanks, Caprihorse.
Bigger tires doesn't necessarily mean bigger wheel size (15 or 16 inch). You could have 37 inch tire fitted on a 15 inch rim and fitted properly. When it is said "bigger tires" it is meant for bigger rubber intended for wider footprint and ability to float easier. Add to that that whatever lift you have on a solid axle vehicle would give you zero additional clearance. The only thing that can raise the axle a bit higher for more clearance is a bigger tire.

I understand your perspective regarding safety, which is sensible.