okie981

+1

I would pay my money for a taller 1st gear and shorter 2/3/4/5. But I don't track the car, never have, so I'd probably have a different preference if I did. For street driving, I want taller 1st, shorter 2/3/4/5, taller 6th for a 2,500 RPM cruise at 70 to 75 MPH.

Bardman

If we focus on street driving, I think this is very simple.

Where is the "fun" zone for the GT4 engine? From 4k rpms upwards. (IMO due to the torque dip below that, and the way the exhaust valves open at that point the GT4 engine is not really fun below 4k rpms)

Can I drive at road legal speeds with the engine at 4k rpms upwards? Unless I am on the highway, I can get about 1-2 second maximum burst of 4k rpms and higher in second gear before I am way over the limit.

Driving at high rpms in first gear is not fun.

In order to access the engine sweet spot at speeds that are closer to road legal, the gearing in general needs to be shortened.

I am 100% in agreement with stout, unless engine mods change the sweet spot to lower in the range (which to my knowledge, none of them do), they will in no way make the gt4 more fun on the street (in many cases they will just make it worse as you will be going even faster before you hit the sweet spot).

The best "fix" for this car for street driving would be to shorten 1-5 and keep/make 6 extra long to make highway cruising more comfortable.

mark kibort

You guys just ruined my street drive (same GT4 ratios) .. now i see the space from 1st to 2nd as being annoying now...

also, Ive also never liked how grabby the clutch is in 1st due to the super short 1st gear. Guess its good for traffic jams for just crawling around without having to punch the clutch so much......... but taller 1st would put 1st and 2nd closer, but still not deal with the street desire to use MORE gears. then, i guess, you could put in a shorter RP............ but then you need a taller 6th.......(because my main requirement is to have low highway RPM in top gear.) mainly because 6th is a toss away gear and is too close to 5th as it is, due to the wide HP band... using it as an overdrive only and having 5th go to 155mph would work well.

Thats my final thought on the topic.

Enjoy
Mark

Mike J

Don't agree - this is a clearly a street car that can be used as a track car, not a track car first. The Clubsport is the track car. But either way, its not stated anywhere by Porsche from what I have read or seen.

Ok, flame proof clothing on!

Cheers,

Mike

stout

Yes, yes, and yes re: some key folks at PAG.

This was indeed my reason for this thread—to see what kind of real demand is out there, and whether a vendor or two might be willing to meet that demand...as well as what it would take to get them to.

The other hope was to determine what ratios are needed to replicate 1-5 and 7 in the 991-1S with the GT4's R&P. There may even be a slightly better setup for the GT4 in the 1-3 range, but my gut says the 991-1S 1-5 would be a nice upgrade on the street, autocross course, and some tracks too.

That's my gut.

GT4 Clubsport is a 2.7 PDK gearbox with 7th still in place but locked out, making it a six-speed gearbox, and yes I think it's gear set is better than the GT4 gear set mainly because Porsche got seven gears to work with rather than six, and because the 2.7 gearing seeks to more aggressively multiply the lesser torque of the 2.7. With a 3.8, it probably makes for a nice push in the back. Still need to drive a Clubsport.

Fully agreed!

I'm less sure about 1st and what's best there—and turn to Bill and Matt and others for thoughts there—but the gearbox you describe above sounds like just the ticket. The 3.8 can easily push the Cayman down the road at 70-75 mph on fewer rpm—I'd just look to match the 7th gear characteristics of the 991-1S, even though there my be a sight tweak that would be better for 70-80 mph efficiency. It would probably take a lot of testing to figure out how to realize any gain over the govt-regulation targets that 7th gear was designed to meet.


It is of course just a gut feeling based on a lot of experience, but my SENSE is that this upgrade could create a similar kind of magic in the GT4.

Yes, I get this logic—for track work. On the street, I am actually very happy with the GT4's power over 5000 rpm. I just want to get up there more often, and more quickly in the lower gears. Only 1st allows you to get there legally, and maybe second. MAYBE. That's crazy—for public roads.


Sorry about that!

And thanks for the PMs. Good stuff, and all good.

Thanks also to Matt, Bill, and others who have contributed to this thread. I take leave for the evening with a request for those who are handy with gears: What set of ratios would replicate 1-5 and 7 from the 991-1S while keeping the stock GT4 final drive? Maybe I missed that in pages 12~ to 20.

docfink

Well, I still really dig it, and I've noticed the 1-2 drop also, but I find the car responsive around town and on the highway. Considering my commute is only about 6 miles, I barely warm the car up daily anyway...However, I'm now going to bury myself in the sand and try to convince myself I have a great car...then let my dealer know that, while I intended to keep this car for the long haul, please put my name on the list for its replacement, as I reckon gearing WON'T be an issue for the new one!

Kidding aside, I won't be performing surgery on the blue beast anytime soon. I still get excited every time I look at it, sit in it, and rev it up.

The complaint about my previous turbo was different, but similar: "you can't utilize all the power, and only in short, safe bursts when possible". Nothing's perfect, but the GT4 is pretty close.

Jimmy-D

All in all the gear ratios really do not bother me. Yes - shorter 1 thru 4 would create a master piece but the car is still great. Every sports car out there has their vices

okie981

My last post on this thread has to be taken in context of what I would change if I were to change the gearbox. That post is not to say I don't love driving the car, I do, it's so much fun to drive in stock form, it make me smile several times each drive I take, and sometimes makes me laugh out loud 😃.

mark kibort

Well, i should have been more clear... you know i know what a "track car" is.... my point was the design, of this porsche and many others comes from the track.. and usually, in most ways, you make it comfortable on the track, it will be comfortable on the street (as far as power distribution, not ride, etc ) So, the gears are perfect on the track. i say this , because there are many tracks and no way of making it perfect for one, so they made it pefect for all. on the street, techically, its perfect too. that gap in 1-2nd is not that great and how often are you WOT shifting into 2nd on the street? and if you are, are you pointed straight? are you on street tires? it all points to having a little safety margin by not dumping the car into max HP (aka: max rear wheel forces) as you speed shift into 2nd. this probably how most accidents occur..... anyway, on the track, its not needed sans for a brief fraction of a second out of most slow corners. so, just shift the car short on the street, and enjoy the very short 1st as it is... use 2nd and 3rd gingerly, as i do on almost perfectly similar car of my own (same gearing and HP) and have fun.

sure , the gap could be closed from 2nd to 3rd, but its actually not even being discussed as an option.. 3rd-5th is... and , with the power band of the GT4 being so wide anyway, i don't see the point as it is 97% optimal (from a power and acceleration perspective) as you can possibly be. you saw the data, with the stock power curve being used, advised changes made a 1.5% difference in usuable rear wheel force. (slightly more using "other " dyno output) and even less when you average the trade off as you row the gears.

edit: i meant to say, "1st to 2nd" was not being discussed. But , yes, Matt and others are right.. there is a little room for improvment for the gap of 2nd to 3rd.. ill agree. 7700rpm dropping to 5600rpm is not optimal, as small as the problem is... so a lower 3rd for closing the gap is a good idea that Matt solves!

so, enjoy it. be happy it's one of the best cars out of the box around. spend time driving it, rather than trying to fix something that isnt broke. remember , perception can be reality... try and focus on how great it is, and the street function will be satisfactory as well.

GrantG

That's exactly what's being discussed. Adding a lower/closer 3rd-5th will tighten the gap between 2nd and 3rd (and 3rd to 4th and 4th to 5th).

GTgears

For those who missed it (mark) the top set up is what SW customers have been installing.

stout

Cross post from the other thread, just in case someone needs a breadcrumb in 2018 when it's time to regear their GT4.
https://rennlist.com/forums/gt4/8847...t-world-5.html

65-70 mph for top of 2nd gear seems like the sweet spot to me.

There's an interesting thread on another (competing) Porsche forum among 991-1S owners complaining about the MT's third gear tweak vs. PDK, called "Disappointed in 7mt gear ratios". Like them, I cannot figure out why Porsche tweaked 3rd unless it was to give PDK a clearer performance edge for marketing reasons? One poster over there figures the ratio change moves the 2-3 shift drop to 7800-5800 rpm vs 7800-6100 rpm with PDK. More food for thought.

But if custom gears are needed, Matt's approach of working from second gear outward is the right way to optimize performance in gears 1-5. And 65-70 seems like the sweet spot.

stout

GT4 as is...is surely great. One of the greats.

That said, those of us with any time in GT3s know it doesn't have some of the "big personality" and straight-line get up and go we're used to in GT3s. Hard to complain (!) at the price, but having driven the SW GT4 1.0, I think the following would make the "masterpiece" you mention above:

-Optimized gear set 1-5 and taller 6th
-LWF (really liked this a lot...a little less pedal effort but more mechanical noises to enjoy a la 997 RS—if you are into that kind of thing, and I am)
-Headers

I can't see modifying the suspension and brakes. They are seriously good out of the box. The only exception for me might be pieces needed to optimize the alignment for individual preferences/uses.

The GT4 is without a doubt a GREAT sports car. And it sounds like the three improvements above could add $20k to the bottom line. That means they won't be for everyone, but I think they may be well worth it for some.

mark kibort

sorry, i meant 1-2nd 2nd to 3rd is near optimal now for the HP spread.
by changing the gear ratios, it becomes not as optimal at a track like laguna or sears because you then cant take 3rd to redline, or near redline on two critically important straights. you get an awkward shift point, that many at the track will not want.

Sure there is a very small gap between 2nd and 3rd.. very very small. we talked about it before .. its 72% of redline RPM drop.. that gets you to 5600rpm from redline.. if your target was to speed time in the 80 to 90mph for a good period of time... say, a few turns on a track had peak speeds of 90mph, then it makes perfect sense. conversly, if those tracks had more time at 100 to 110mph, just the opposite would be desired. however, ill agree, that bringing them closer together is a good move, at a price obviously... but thats the price of near perfection.

the trade off might not seem obvious. you say, "wow, i just put the gears perfectly straddling the power band, what could be a trade off? the trade off is then only going to be track specific.. i use Lime rock or laguna seca approach to the corkscrew. lime rock uphill /downhill could use the stock GT4 3rd from 6k to 7,500rpm perfectly. make it shorter and you are grabing 4th, possibly out of the power band, but forcing a time consuming shift, would be my main complaint as a racer. same thing at laguna. you run up to redline with a shorter 3rd, and then have to shift, still in the power band, but you need to shift.

there may be a track with just the opposite situation or other turns and straights at that track, but you get the idea..........

now , straight line, infinitely desirable speed ranges..... sure, tighten up 3rd gear and bring the others along too.

you got it. yes, but actually the sweet spot is from 55 to 80mph, because that is your max HP range.... Randy pobst (and many of you know randy) drives he GT4 at laguna. makes some interesting comments. (surprising, as i know randy and we have had these discussions before at the track ) he talks about the long gears. well, its funny because he has raced cup cars and others with the same gearing poings and never said anything. maybe the GT4 guys talked to him first, you think. anyway, if you watch the video, he is shifting take taking perfect advantage of the engine with the gear box.
downshifts to 2nd around turn 3, upshifts before 4, runs it to top of 3rd and 4th before turn 5, downshifts to 3rd (could be 2nd but he didnt), runs 3rd to the top of the hill before corkscrew. (again, why would you want a shift there), nice downshfit to 2nd down the corkscrew.... runs up to 3rd.. ..............etc.. he does eactly what he should do with the car and there is litle room for improvement at that track , with that HP level and those tires.

by the way, it makes Joes lap VERY impressive there on RE71Rs which are a 200treadwear tire vs the Michiliens sport cupIIs that Randy is driving on for the test running only 1 second faster than Joe. (nice work Joe... what could joe run on a set of real DOTs? i bet faster!! )

Da Hapa

Absolutely love my GT4 and as another owner that views his GT4 as a street car first and foremost, I absolutely agree 100%.