Performance Issue (4.08 Rear End?)

[Clyons0203]

I have always noticed an off the line performance issue with 1rst gen Qs. They are dog slow off the line. Weight + Nissan's strange gearing + little timing advance in lower RPMs = slow, but smooth off the line.

I want to increase my Qs off the line performance. I already have the 91 octane NICO ECU.

I recently raced my cousin 05 350Z auto from 30mph to 100mph and the Q was in front the WHOLE time. At 30mph in 1rst gear the Q is right at the beginning of the power band. She jumped ahead of the 350z and spread a gap when I shifted to 2nd. The 350Z was closing the gap from 85-100, but the Q was still ahead at the end. But if the race was done from 0-100 the 350Z would leave the Q so bad off the line I would never be able to catch him.

So I can either:A - swap a 91-93 transmission with lower gearing (too costly!)B- get the MAD MAX NICO ecu and hope for more off the line performance (will do!)C - get a billet torque converter (too costly!)D - do some research on the 4.08 rear end (will do!)

I really dont want to pay to drop\replace the transmission because my transmission is in good condition with good service history. And I am sure I can handle swapping rear ends with the tools I have.

Now any updates on the 4.08 rear end deal???

[ScottJackson]

Well, I did a 2.81 to 3.91 with LSD into my auto 540i BMW. It did give it some more snap off the line, but only for the first 10mph or so. After that it was marginally quicker acceleration. However, seems like the guys who've went to the 4.08 here like the results. If it were me, I'd go with a higher stall torque converter and small wet shot of nitrous. I don't know what the Nico ECU does to the timing in the lower revs, but with my stock ECU in my '93 Q I bumped the initial to 18* (maybe 19*) and it has noticeably better response off idle and gets 22-24mpg compared to 19-20mpg before. I've been itching to put a domestic V8 in the 6L range in my '92 active Q, but I just may try the turbo route first since I have a turbo and my '92 Q needs injectors anyway. There's certainly more roome in the Q than the 540i for a turbo and the Q only weighs about 80lbs more (I was shocked as I expected the diff to be 200-400lbs). I'm waiting for more results and such with the two other turbo builds on this forum though.

[Jeff Williams]

The Mad Max ECU won't help you off the line. At least the tune I have won't do it.

The 90-93 transmission might help. I am building one for Lola right now.

The Billet TC will do a great deal towards making the car quicker off the line. Lola will get one of these with the new transmission.

The 4.08 rear will do it as well, but you will loose some top-end (if you ever use it). I have a 4.11 sitting on the garage floor waiting to go in her once I have the transmission in and have done a few passes first.

[Q45tech]

The 15.4% higher ratio may not improve your zero to 100 time because you will just be shifting 3 [2] gears vs 2 [1] stock because redline will be reached at a 15.4% lower speed in each gear so 2nd WON'T take you to 100 mph as it does with 94-96 AT and 3.538 and you will loose ~~<1 second shifting into 3rd.

Same with quarter mile in 90-93 Q with a raised redline [nico ecu] you can finish quarter in 2nd gear at 97-98mph at 72F ambient and sealevel.

One must always remember these early [prior 2002] were not built for speed shifting but luxury smoothness.

Now once you reach 3rd gear you are 555 rpm per 10 mph so accelration from 90>120 is a tiny bit better by 2.5% [cube root of 15.4%]...0.2>0.3 seconds.

[Clyons0203]

The Mad Max ECU won't help you off the line. At least the tune I have won't do it.

The 90-93 transmission might help. I am building one for Lola right now.

The Billet TC will do a great deal towards making the car quicker off the line. Lola will get one of these with the new transmission.

The 4.08 rear will do it as well, but you will loose some top-end (if you ever use it). I have a 4.11 sitting on the garage floor waiting to go in her once I have the transmission in and have done a few passes first.

Where did u get that rear end from and how much?? does it have the correct abs sensors and companion flange?

[StarPD]

Readers, be aware that while bumping static timing will help the G50, that's not necessarily the case with F50s. My '94 Q45t benefited a lot from bumping timing 3 degrees. When I tried it with my '05 Q45, throttle response, acceleration, and fuel mileage suffered. I had it changed back to stock, and it runs fine now. Both cars used the same fuel from the same station.

Not sure why this is the case, maybe Q45tech has some insight.

As for lower rear axle ratios, Q45tech is correct. While some might disagree with him and claim that their car is a lot faster with lower rear axle, you can't argue with arithmetic. Also, it will lower fuel mileage and increase engine wear over a long period, probably in the same percentage that the ratio is lowered.

Personally, I don't care for higher stall speeds. It makes the engine rev up farther before the TC engages fully, making it feel like it has one of the old "Powerglide" or worse, "Dynaflow" trannies.

Best bet all around would probably be to start your races manually in low gear, or get one of the ECUs or TCU that allows first gear starts. No decrease in fuel mileage, no excess slippage in the TC, no increased engine wear, and no running out of revs before you run out of speed in each gear. Gear ratio spreads in the transmission may not agree with a lower axle ratio either, but that's another story.

Keep us posted as to what you decide, and let us know your results.

Good luck.

[rsiwicki]

I have done 1/4 mile testing with and without the 4.08 under identical situations and it was only 1 week apart. My ET's were exactly the same...I did like 5 passes with and without and the average difference was less than 0.05 secs but interestingly enough my trap speed dropped by a consistent 3mph with the 4.08. So...over the long haul 1/4 mile...it will not improve your ET's. It does make the car a little more peppy around city driving and also really helps with the dreaded "dead zone" in the transmission not down shifting when going like 32mph where you are stuck in 2nd gear unless you manually downshift it which means you have to be really ready to get on it, etc.

i just had custom half shafts made for my 69 vette....cost was $400 and these are sweet in that they are "slip shafts" which means there adjustable length and I no longer need the half shafts as a supporting member as I now have a 6 link rear suspension system. Anyway...I asked the guy out of curiousity if he could make custom half shafts with the CV joints and different flanges as I always thought it would have been so much easier to get this done vs. my $1,500+ 4.08 diff that was built. Seriously one of you all need to go to a serious driveline shop and have them make up a set to accept the 300ZX NA 4.08 diff flanges. I had to go to 3 different driveline shops before I found what i was looking for on my vette but this guy new his $hit and said a set of those could be made for around the same price of $400. A used 300 ZX NA 4.08 diff will run you about $100~$200. Also....even as modded & fast as my Q was...I got my a$$ handed to me 2 times off the line from a 350Z and a few other cars. The Q will never be a good off the line car and you therefore IMO you should only stick to the races/strengths that suite your Q the best.

Btw...I was spotted by a long time NICO member on South Beach cruising on Sunday morning by Lougiez (sp?) the other weekend. He saw my car and sent me an email asking if that was me. I have never met him and have not talked with him in over a year but it was good to hear from a fellow NICO member.

[elwesso]

ROB! I knew you still lurk....

Ive driven robs car (4.08 with stockish TC) and my car (stock rear with high stall TC). I like the high stall TC's better.

At the end of the day, you are going to spend AS MUCH if not more to put a 4.08 in a Q, and I guarntee it will be way more hassle. TC is a swap anyone with half a brain can do.

[NOR*CAL 916]

ia have the r32 skyline gt-r diff, its bolt on and its a 4.11 gear ratio not to mention its a clutch type lsd. i cant get the asb to work since skylines have the abs rings both sides of the shafts while the q has it at the companion flange. driving improved overall city and highway. i can now smash the gas pedal from a stand still and leave two roasting lines in the asphalt, the stock 3.53 gears would NEVER do that. i can get one for you for $500 plus shipping, let me know if your interested.

[Q45tech]

To get the numbers I mentioned earlier one needs a Nico./JWT/Stillen ecu with 7300 rpm redline and a good transmission that shifts fast

If 30 extra Ft/lb or HP is need to reduce quarter mile by 0.3 sec don't go wasting even 0.1 sec with a longer or extra shift.

[Rex]

Ive driven robs car (4.08 with stockish TC) and my car (stock rear with high stall TC). I like the high stall TC's better.

Did you ever post up a time slip to compare to Robs?

[elwesso]

im saying from off the line performance, plus you have an unfair advantage with the headers.

[Q45tech]

All these things were discussed in numerous magazine articles back in 92-94 when Stillen, Wolf, Goldrush, Dynan was selling ecu, tcu, exhausts, nitrous, and 4.083 diffs, etc.

They built numerous show Q with all the mods we discuss.

Things haven't changed much since the gains/loses were the gains/loses.

Plus these were FRESH ENGINES/trannies not time abused.

Plus US gasoline was more likely to be up to spec than after 2000.

[Rex]

im saying from off the line performance, plus you have an unfair advantage with the headers.

I was just messing with you.

I think the off the line when you drove it was already suffering from the transmission that died months later. It now has a stock TC in it and it's def not as peppy "off the line", but still takes off when it down shifts like nobodies business .

[Q45tech]

Why would aftermaket or homemade headers help and not hurt the below 4,000 rpm performance.

Until the back pressure [per unit of time] starts to create inversion nothing is to be gained.

Engineers design for peak torque at some reasonable rpm and then deal with HP.

Design fundementals are pretty obvious when published torque exceeds published HP in English units.

When you see the converse: higher HP than torque you know they are creating numbers for magazine sales......................my horsey organ is bigger than yours.

[Rex]

Why would aftermaket or homemade headers help and not hurt the below 4,000 rpm performance.

Until the back pressure [per unit of time] starts to create inversion nothing is to be gained.

Engineers design for peak torque at some reasonable rpm and then deal with HP.

Design fundementals are pretty obvious when published torque exceeds published HP in English units.

When you see the converse: higher HP than torque you know they are creating numbers for magazine sales......................my horsey organ is bigger than yours.

Dennis - the before and after dyno sheets show an increase in TQ ~4k.

I'll be in ATL this weekend and would gladly let you thrash on the car if you're interested.

[Q45tech]

BUT, with a 4.08: 26 mph is 4,000 rpm, as it is 30 mph with a 3.538.

That is my point nothing but Nitrous [or weight reduction] can help much below 25-30 mph.

Too much Nitrous will just smoke tires leaving you worse off.

Radial superchargers don't really boost much below 4,000 rpm

Higher stall speed TC have so many downsides on street.

Since the 60's engineers have known that for a 4,000 pound car 3 gears [in the quarter are ideal].

Notice the 2007 5AT setup in M35 3.538 diff;First Gear Ratio (:1) 3.84 (with conditions) Second Gear Ratio (:1) 2.35 (with conditions) Third Gear Ratio (:1) 1.53 (with conditions) Fourth Gear Rato (:1) 1.00 (with conditions) Fifth Gear Ratio (:1) 0.84 (with conditions) Reverse Ratio (:1) 2.77 (with conditions) Final Drive Axle Ratio (:1) 3.54 (with conditions)

13.58 TOTAL 1ST GEAR + DIFF

vs 9.85 FOR 90-93 q45

38% LESS REAR TIRE TORQUE IN 1ST GEAR50% less IN 2ND GEAR

The point is 15.4% [4.083] is along way from 38% or 50%

[Q45tech]

By now I would assume ALL NICO members have a NICO ECU to gain the 25-30 lb/ft [flywheel] after 3400 rpm.

[rsiwicki]

yes yes....I one of my dreams was to always meet up with Dennis and let him have some fun with my Q. That certainly would be some fun to hear how the engineer thinks about my former car.

[StarPD]

Q45tech, you briefly referred to an oft overlooked way to improve all aspects of enjoying our Q45s, that is, weight reduction. It improves acceleration, handling, ride, and fuel mileage, and has no downsides or disadvantages. A 200 lb weigtht saving can provide excellent benefits. It can be accomplished fairly easily.

*Removal of the spare tire (I haven't used on in over 15 years).*Replacement if thge battery with a lightweight gel type (and relocating it to the trunk gives additional benefits in ride and handling).*Lighter wheels and tires (which would further improve ride and handling)*Lighter exhaust system, especially with headers)

There are other weight-saving tricks, but once these improvements are done, further gains become more difficult and sometimes more expensive.But imagine another 100 lbs off the car, for a total of 300 lbs reduction by removing other non-essential components or replacing them with lighter ones. Old racer's saying: "Take care of the ounces, and the pounds will take care of themselves".

I'm curious as to what you would calculate for acceleration improvements 0-30, 0-60, and 1/4 mile elapsed time and speed. with both a 200 lb and 300 lb weight reduction on a G50 and an F50. The one thing that wouldn't improve significantly would be top speed, but Q45s are pretty fast already, and in good tune should hit around 155, maybe more.

[ScottJackson]

I still think the higher stall converter is the way to go. Nothing crazy, but something in the 2000-2500rpm range would work well. I know my rear diff swap didn't do a lot for my bmw. I think a lot of guys feel it helped make the car faster, but it didn't do much but bring in the first shift sooner (and they probably like to justify their efforts to some extent). As has been said, other than nitrous or torque converter you won't get a big off the line punch. And you better not try spraying nitrous coming right off idle unless you like to see what an intake's insides look like (not to mention the likely broken pistons/block also). A roots blower should come on pretty quickly, but with a stock converter it'll still take a moment to really start huffing. I really think more displacement with higher stall converter is the way to go. With a lockup converter, I don't think a little extra stall is a bad thing on the street.

[Clyons0203]

ia have the r32 skyline gt-r diff, its bolt on and its a 4.11 gear ratio not to mention its a clutch type lsd. i cant get the asb to work since skylines have the abs rings both sides of the shafts while the q has it at the companion flange. driving improved overall city and highway. i can now smash the gas pedal from a stand still and leave two roasting lines in the asphalt, the stock 3.53 gears would NEVER do that. i can get one for you for $500 plus shipping, let me know if your interested.

I think some Q have the ABS rings on both sides of the shafts too. Hicas, Traction control, or active suspension one of those options required for infiniti to put the abs rings on the shafts. Or maybe it was a mid year update. I remember hearing about it.

With that sensor not working, I think the ABS system will disable itself. What you could do is short the rear sensor and this will allow ur front brakes to have abs. The front brakes do all the work anyway.

[Q45tech]

A TC's stall speed is a function of engine torque curve/amount at a certain rpm. Increase the torque produced and the stall speed increases.

With a normal engine at normal altitude and ambient temperature the oem TC stalls at 2200 rpm.....................the viscosity of ATF greatly affects the speed with is itself temperature dependent.

[silver2k2]

I think some Q have the ABS rings on both sides of the shafts too. Hicas, Traction control, or active suspension one of those options required for infiniti to put the abs rings on the shafts. Or maybe it was a mid year update. I remember hearing about it.

With that sensor not working, I think the ABS system will disable itself. What you could do is short the rear sensor and this will allow ur front brakes to have abs. The front brakes do all the work anyway.

Traction Control equipped cars have 4 channel ABS

On the G50 the front and rear brakes share equal % of the stopping, this is different from most cars

[StarPD]

I think some Q have the ABS rings on both sides of the shafts too. Hicas, Traction control, or active suspension one of those options required for infiniti to put the abs rings on the shafts. Or maybe it was a mid year update. I remember hearing about it.

With that sensor not working, I think the ABS system will disable itself. What you could do is short the rear sensor and this will allow ur front brakes to have abs. The front brakes do all the work anyway.

Not so. While the front brakes do indeed do most of the braking, better to lock up the front wheels than the rear. That's why when pickups first came out with ABS, it was on the rear only. Blow a rear tire at speed, or lose the rear end in a powerslide and you'll quickly see how this works.

Trust me, if you have to eliminate ABS on one axle, don't do it on the rear.Heavy braking also unloads the rear wheels, making them a lot more prone to losing traction, and swinging the rear around the front. Not fun trying to regain control once the rear end breaks loose unless you have much experience with extreme high speed cornering, and can safely drift a car through a fast corner. Even so, losing the rear in a panic stop situation is sure to give one a thrill, if one survives.

[sheadee240]

I have a 94 q45T with traction control is it possible that this r32 gtr diff would be a direct bolt in and allow plug and play use of abs and tcs.

[ScottJackson]

I mostly disagree. You need the front tires to rotate in order to turn the vehicle. It's much more important to have ABS in front than back for most purposes. The only thing that is somewhat correct is that the rear tires will be more likely to slide as the weight comes off them in a hard braking. However, rear ABS is only better than front ABS when there is basically no chance of the front tires locking up and a high chance the rear tires will.

As per this topic, Tech has shown (and my experience confirms along with others) that going to the 4.08 won't make the car much faster at low speeds... or high speeds. It will eat some more gas and create some more engine wear. I didn't realize the stock converter was as loose as it is. I think 800-1000rpm over stock stall would be great. High stall converters can feel a bit mushy, but will usually get you substantially better launch off the line, if the tires can hook it. With a lockup converter, it shouldn't hurt your cruising at all to go with higher stall.

[sheadee240]

ia have the r32 skyline gt-r diff, its bolt on and its a 4.11 gear ratio not to mention its a clutch type lsd. i cant get the asb to work since skylines have the abs rings both sides of the shafts while the q has it at the companion flange. driving improved overall city and highway. i can now smash the gas pedal from a stand still and leave two roasting lines in the asphalt, the stock 3.53 gears would NEVER do that. i can get one for you for $500 plus shipping, let me know if your interested.

I'm not sure if the statement that the lsd is a clutch type is correct. I found one for sale that claims to be from a r32 gtr but it has a sticker that states viscous lsd on it. I do not race my Q but I do find that it is missing some off the line snap for my taste.

[96Qowner]

Have you seen this thread?

Everything is set if you want to order your R32 GT-R LSD 4:11

Good discussion of possible differentials for the Q45. R32 GTR GTS R33 R34

[Haitian_King]

I've heard about the Skyline 4.11 rear end. My friend told me that unless you're good with a micrometer and the 4.11 is lined up PERFECTLY, if you mash the gas, you'll blow your rear end all to hell.

This is what I was told last night. He was a little drunk, but I think that's correct right?