Topic: Help me to reduce my drag racing times

[Kelu]

Hi guys, as you could see in my reports from my drag races I'm always trying to improve my times. So far so good, my strongest point is the launch, only one car with one axle drive launched better than me (a Porsche Cayman), I have launched better than many stronger cars than mine.

My problem is at the end of the race, last 30-50 meters (100-150 feet) of the race is where I suck and I suck big time. This happened all the time no matter the tires, surface or my mods. The point where I start to loose my advantage is top of 3rd gear, shift into 4th gear and few seconds in 4th gear, I can feel the car not pulling in that period. Right before the finish line I feel the car starting to accelerating again but is too late.

My presumptions for this issue:
a) Huge amount of time to wide open the throttle and rebuilt the boost. See my issue in this post: http://www.kappaperformance.com/forum/index.php?topic=4505
Possible solutions:
- GMPP using No Shift Lift (if this will be proved to work on an Opel GT)
- WOT Box (Launch control and NLS): http://www.streetunit.com/Wide_Open_Throttle_Control_Unit_p/n2mb-10.htm
- SpringBooster for faster wide throttle opening but it will still close the throttle between shifts so still delay to rebuild the boost

b) Gear ratio of 4th gear, I know is 1:1, I test it and that gear is hugely long, from 80km/h (50mph) up to  220km/h (130mph), there is no way to open the gearbox and change that. Differential can be modified to change this from 3.71 as we have now to a 4.1, but this might be too hard to accomplish because I don't know if I can find parts to modify stock diff and I'm trying to avoid that. I have used smaller wheels but that made even worse, made me to shift into 4th gear even sooner. If I would use bigger wheels will keep me in 3rd gear? What wheels I need to use to reach 7200rpm into 3rd gear a speed about 110-120 mph?

So any ideas to fix this issue?

Here are some video for see it with your own eyes (all lost because of that issue):
http://www.youtube.com/watch?v=0ljJXlqJFzk&playnext_from=TL&videos=V1_uVMtCXiU
http://www.youtube.com/watch?v=91bp4GnHQRU

[NormSky]

Looks like you've covered everything possible. I'd look for a 3.91 base kappa differential, raise rev limiter, and change tire sizes. You could also lower your car for better aero dynamics. Are you allowed to put the top down? This would help with aero and put more weight over the rear wheels.


Norm

[shabby]

Possible solutions:
- GMPP using No Shift Lift (if this will be proved to work on an Opel GT)
- WOT Box (Launch control and NLS): http://www.streetunit.com/Wide_Open_Throttle_Control_Unit_p/n2mb-10.htm
- SpringBooster for faster wide throttle opening but it will still close the throttle between shifts so still delay to rebuild the boost

Dont bother with the sprintbooster, it won't help you at all.
First thing i'd do is try to do a write entire of a gmpp tune onto your ecm, there's an 08 kappa available here http://gatewayecotec.com/
If the write is successful and the car drives fine(you'll get a barometric sensor check engine light though) then you can order the gmpp sensor from werks and install them.
If that doesn't work then the wotbox is your only other solution to fix the lag in between shifts.

[Gentleman Jack]

Kelu-
Perhaps adding a rear wing like Arabas?

What is your red line now?  Someone just had theirs bumped way up but you are already at 7200... not sure how much more you can go.  Is there still power to be had at 7500?  That may be all you need, stay in 3rd to 7500?

GJ

[KWhale]

And Stripes Kelu....I'm telling you stripes makes you faster too!  Black stripes are the fastest.

GJ, there is no real worth in revving these engines up as high as you're asking about.  When I had my car at Westers for the tune, you can see the HP and Torque fall off the table once you rev past about 5,200.  Here's my before and after dyno to show you:



The no lift shift would be your best buddy I think Kelu.  I also do not know if that is built into the Westers tunes or not though and would be afraid to try it just to find out I don't.

[Gentleman Jack]

KWhale / Kelu,

Yeah, I thought that might be the case.  How tough would it be to swap rear ends with a NA?  Or does that go the wrong way?  Not that it is readily available for Kelu...

NLS would help if it can be done repeatedly with success.

And, I think Kelu already has stripes?  Or graphics of some nature.  So, that's not the answer.  Perhaps wrap the whole car in White Vinyl? 

GJ

[Kelu]

NormSky: There are no NA Opel GTs, Opel GT is only LNF so this might become pretty expensive. Isn't LE5 differential weaker than LNF one? Already rev upped 7200 or 7500rpm iirc. I need to calculate if changing the diff ratio and the wheel size to be sure I can stay in 3rd gear. I'm working on the suspension mods, this will include coilovers and I will drop the car too, I'm not allowed to race with top down.

shabby I was thinking same about SpringBooster. There is another Opel GT who is waiting the 3 Bar sensors, I will check his experience with GMPP and maybe do it myself too, I need to talk with Lyndon about this too. I already ordered WOT Box, even GMPP will work, WOT has launch control too which will make my launches very consistent.

Gentleman Jack There is no power above of 6500rpm from our engines. See my dyno: http://www.seorom.ro/gt/gt_opel_exe.jpg

KWhale I have black stripes  looks like you didn't checked my pictures.

Does someone have our gear ratios? I remember I saw them but can't find them anymore, I will try to calculate what tires I need with stock diff to stay in 3rd gear.

Going from 3.71 to only 3.9 i have the feeling is a too small difference to worth the money (1500-200$), I was thinking to 4.1 to really change something, am I wrong?

[Arabas]

Kelu, i had the same problem in racing, even though my car was stronger than another GT i.e., when shifting from 3rd to 4th it felt like the other car was approaching me (or if it was a GT as powerfull as mine, i was left a bit behind) and then, after a couple of seconds in 4th gear i was back at the good power, leaving the other car far behind, or approaching the other car (the later in the case i was racing with one of similar hp).
then i talked with Kagem and decided to experiment. Kagem has rev limiter at 6500, mine is set at 7000.
so we raced and i shifted at 6000-6200 rpm.
this made a significant difference on the result. as you said, our LNF's behave much better if you shift at 6-6,2K. more revs will probably give you less power, plus when you go in 4th gear the rpm's will be better.
what rpm do you shift? it's worth trying this..

[Kelu]

Arabas: last night I was thinking to same idea. I was encouraged to think about shifting around 6000-6500rpm max because of the GM which decided NLS to be made in that rpm range. I generally shift around 7000rpm (200rpm more or less) but I'm sure GM have strong reasons to make NLS in the 6300rpm area. But then again, damn 4th gear will come sooner.

I have watched Cobalt community drag racing report, even they have slightly better 4th gear ratio (shorter than our 1:1) they try  to stay only in 3rd gear with tuning of the wheels. There were 12s second ET with same mods as me.

[Arabas]

Kelu, if you find a solution with the gearbox, pls share, all of the Greek GT owners will thank you (and if it is of value under 500euro) then we will do more than just love you   
now, don t get excited, i m just kidding...
for sure Kelu, you should try shifting BEFORE 6500 rpm. try this on the first chance you get and you will see quite an improvement.
the tricky part is to convince yourself at that time to JUST DO IT and not get too excited and deny shift because "I still have 700rpm left, no need to shift, no need to shift, no need to shift!!!!"
Just shift around 6200 rpm and things will improve.

try this and let us know
 

[Kelu]

300-400E will cost only the labor to get the gearbox removed and re-installed, so no solution for gearbox for that kind of money.

I will try to do that racing some of my friends who are close to my performance and I will report back. I know it will be hard to convince my brain to shift at 6200rpm but I think I will manage that, I wonder what will be the rpm in next gear, I hope will be above 3000rpm after shift at 6200rpm.

[NormSky]

The Getrag differential casing is the same for a number of GM cars. The gearing is changed. You could look at a 3.42 or 2.93 which are inter changeable but you loose acceleration with the taller gearing. You just have to make more power to compensate. 


Norm 

[Kelu]

What? Change the diff and get more power? Norm what are you trying to say, worst solution possible?

NA Kappa:
Final Drive 3.91:1
1st Gear Ratio 3.75:1
2nd Gear Ratio 2.26:1
3rd Gear Ratio 1.37:1
4th Gear Ratio 1.00:1
5th Gear Ratio 0.73:1

LNF Kappa:
Final Drive 3.73:1
First 3.45:1
Second 2.21:1
Third 1.59:1
Fourth 1.00:1
Fifth 0.76:1

Our getrag diff: http://www.getrag.de/en/259

I was wrong, I don't need shorter final drive ratio like 3.91 or 4.10 to stay in 3rd gear up to 110mph, i need longer:
245-45-18 -> 26.68 inch overall diameter

with 3.91 final drive ration: 3rd gear at 7000rpm makes 89 mph
with 3.73 final drive ration: 3rd gear at 7000rpm makes 94 mph
with 3.42 final drive ration: 3rd gear at 7000rpm makes 102 mph
with 3.23 final drive ration: 3rd gear at 7000rpm makes 108 mph

The other solution with the tires and keeping the ratios stock:
275-55-19 -> 30.90 inch overall diameter (will this fit in our back?)
with 3.73 final drive ration: 3rd gear at 7000rpm makes 109 mph

[NormSky]

Exactly! You had tow questions with the results counter acting one another. 

The Corvette guys with twin turbos change out their 3.42 to 3.15 from the automatic transmission version.

Word to the wise the 4-cylinder, turbo or not, is sensitive to wheel/tire combinations. So do your homework. 


Norm

[Kelu]

I think for the moment I will stick with shortening the delay in shifting and shifting sooner.

[KWhale]

I think for the moment I will stick with shortening the delay in shifting and shifting sooner.

I agree Kelu, and this mod costs $0 to do.  I Happen to have the AeroForce gauges in my car now, and they come with the option to set up a shift light warning based on RPMs.  I originally had it at 6,800 but found the power seemed to tail off just before a shift.  I experimented and now have the warning light set to 5,800 RPM.  I know that sounds low, but there is also reaction time after the light comes on, which is putting the revs at about 6,000 by the time I shift.

I do not drag race "officially" so I do not have any time slips to prove anything, but I am 100% certain that the car is quicker with these lower RPM shift parameters!  Think of it this way......if you are shifting 3 times in a race (1-2, 2-3, 3-4) now, you will still have to shift 3 times in a race using the lower RPM shift points, so don't worry about that making a difference.

[LatinVenom]

Kelu:
What you need to do is learn how to power shift and do this at the 6000 RPM. mark for our LNF.
You need to master this in drag racing.
If not you need to get into an automatic transmission and have it modify for drag racing.

[Kelu]

I did some power shifts in some races but only in the 3rd to 4th gear shift. I don't consider it a good option:
- can touch too much rpm and risk of damaging the head not mentioning the limiter
- risk about being locked out of the gear is increasing in this case which can be deadly for the head
- the gain wasn't so great to worth the above risks
NSL is by far better option in this case with pretty same results

[Mac]

changing trans would be very costly mod and if you look at the gearing not much would change, todays six speeds are 1-4(1;1) and 5 and six are OD, the only trans in standard that you can change withany ease is the ROD 5 or 6 speed, many gear choices there but again not cheep, but it does have 1-5(1;1 and only 6th is a OD. since the main and counter shafts are all splined you can change out and make the splits your choice, but again those gears are not cheep. Though they are easy to work on since the case is a two piece sandwich. I have two of them one a Doug nash 5speed no OD and i have the later Richmound 6  but i have feeling they wont bolt up to a LNF with out a adaptor and custom input shaft.

I am looking at the new TCI auto
 the 4L80E-based TCI® 6x Six-Speed Automatic Transmission is a fully programmable transmission that gives you six forward gears (2.97, 2.31, 1.57, 1.18, 1.00, 0.75) THis would be killer 1/4 mile street set up, again not for a LNF without a custom adaptor.

Not for my Sol but my 1971 z28, im tired of footing the 5 or 6 speeds sticks, sucks getting old and cranky, pluss this sound bulit proof too rated at what 800+hp, now do i get the erod ls3 or rebuild my 454? 

[Gentleman Jack]

now do i get the erod ls3 or rebuild my 454? 

rebuild the 454 and add a super charger and two remote turbos.  You should do just fine if you can see.

GJ

[LatinVenom]

I did some power shifts in some races but only in the 3rd to 4th gear shift. I don't consider it a good option:
- can touch too much rpm and risk of damaging the head not mentioning the limiter
- risk about being locked out of the gear is increasing in this case which can be deadly for the head
- the gain wasn't so great to worth the above risks
NSL is by far better option in this case with pretty same results

I do not disagree with your statement the NLS is the way to go but you do not have that with The Westers tune.
So you would have to go to HPT and download the GMPP tune get the 3.0 bar sensors from Werks and then have Westers give you his GMPP/Westers tune.
To me if you know how to power shift then there should not be any problems.

[Kelu]

3bars sensors + GMPP calibration from another car, I'm waiting Kuprito doing that on his Opel GT, i'm not sure if this will work out on Opel.
I will get NLS using WOT box among Launch control, ordered, now waiting to arrive I hope to receive it in time for next race on 6th of June.

Meantime I will try racing my friends to check the differences if I shift around 6200rpm instead of 7000rpm.

After I fix this issue with the delay in shift I will think to a solution how to stay in 3rd gear up to 110mph, there are so many different data about our gear ratio, dunno which I should trust.

[Arabas]

any feedback Kelu?

[Kelu]

No, rains like hell around here so no racing for testing, WOT Box didn't arrived yet, no news GMPP on Opel GT.

[LatinVenom]

What do you mean about so many different data about our gear ratio.
For a manual transmission on a GXP is all the same.
I am not sure what the Opel and SKY have but if they are the same, then base on what we see on the Dyno, the shift at about the 6000-6100 RPM mark would be it. There is no power being made once you reach that RPM with our turbo.