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06-20-2004, 12:51 PM | #1 |
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rev limit, launch rev idea....
Not sure if you can do this but here is my idea....
2004 sti, thinking about installing an msd soft touch rev limit and activating it with the clutch switch. This would give a good launch rpm and also could possibly provide full throttle shifts. I have no idea if this could be done in the sti. I am just not sure if you can run the soft touch in this car without the full msd ignition. 6000 launch rpm rev limit, and 6k rev limit when shifting, alowing for (safe) full throttle shifting. This idea came from a civic that I have using a hondata system with this feature. I e-mailed msd and asked them about it. waiting for responce, Wanted to see if anyone here has done anything like this. Here is the link for the hondata thing....check out the video too, shows it working. Click me! Click me!
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06-20-2004, 12:59 PM | #2 |
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msd does not like to answer questions. this may be bad if using nitrous with a tps sensor activator. why can't you just press throttle a little to launch at a certian rpm? it may work with a unit to change the tach signal to one that will work with the msd unit. a lot of trouble to solve a minor problem. just use the pedal.
also, your computer may not like the fact that your tps sensor will be at 100% while nothing is happnin. don't try it! Last edited by turbo2nr; 06-20-2004 at 01:08 PM. |
06-20-2004, 01:18 PM | #3 |
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I am not sure you understand what i am tring to do. Yes i can use the pedal to launch my car, yes i can shift gears by letting off the throttle and shifting. This is just for more consistant times at the track.
i usually rev from 4k-6k until the last light then floor it and release clutch at the same time....it works for 1.74 60ft times, the problem is getting the 1.7 everytime. Not using nitrous, this sytem works great on the civic, i am just wondering if i can use a simple rev limiter and use the clutch switch or even a nitrous full throttle switch hooked up to the clutch pedal to activate the rev limiter, which if hooked up to the clutch would also work for keeping the go pedal on the floor between shifts resulting in quicker times, more consistent shifts and times. "This allows the rpm to be matched while shifting gears while keeping the throttle wide open, which speeds up gear shifts and helps keep turbo chargers spooled up. Great for improving those 1/4 mile times" "For bracket racing tests have shown that ET repeatability to less than 1/10th of a second is achievable without the use of an automatic." That would be two good reasons for me wanting to do this. Just checking subaru compatability or if n e body has done anything like this. Not to see if it would be easier and cheaper to "just use the pedal" |
06-20-2004, 01:20 PM | #4 |
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how would it be any different then hitting the normal subaru rev limiter and the tps? It is still reading 100% correct? or does subaru change the tps signal when the factory rev limit is active.
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06-20-2004, 01:32 PM | #5 |
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the subarus are the worst car to have for bracket racing. you will lose to an automatic rental car every time. waiting for the engine to drop to an exact rpm will take forever even if you have a rpm limiter. just shift it fast, don't worry , your trans will break anyway.
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06-20-2004, 01:40 PM | #6 |
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when the factory rev limiter kicks in, it controls fuel and timing, at a certian rpm.
using an aftermaket device intended for a carburated car would not be wise. the car would still be trying to spray fuel to match the tps, but no spark, then when you get back on it, expect a huge back fire to explode even after the turbo, trying to spin it backwards. the computer will not know what the hell is going on. |
06-20-2004, 01:49 PM | #7 |
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I'm not worried about the trans breaking, maybe if i shift at wot without a rev limiter then i might be worried about it breaking. The car is stock, if it breaks the tranny then oh well, thats what warrente is for and if it breaks when stock and driven right then i don't want it anyway.
Oh and i didn't get your answer for the stock rev limiter and the tps signal? oh wait i just read that now it controls fuel and timing. Where are you getting this info? who said it was intended for a carburated car? The only problem i see if i can hook this up the car is will it detect a missfire when the rev limit is active. looks like i will have to wait till tomorrow and call them about it. Unless someone else says something. |
06-20-2004, 01:58 PM | #8 |
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it will detect a misfire, but only after a few combustion event cycles, at that point there will be a lot of raw fuel in the exaust. i have tried to get msd to answer many questions, no luck. i run a msd fuel pump booster, the more boost, the more voltage to pump. it is adjustable, and puts out up to 26 volts to pump at a dialed in boost setting. i needed more pump to go from low 11s to high 10s. I have broken everything and upgraded. i use a $10,000 mrt dogbox with a custom made 1.00 ratio fourth gear (22tooth,22tooth) made by brett middleton to go about 133mph @7000rpm in 4th
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06-20-2004, 01:59 PM | #9 | |
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06-20-2004, 02:03 PM | #10 | |
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from MSD's website "Unlike many rev limiters which simply cut off the ignition spark, the Soft Touch uses computer circuitry to drop one cylinder at a time and then fire that cylinder on the next cycle to prevent fuel from loading up the plugs. The result is very smooth rev limiting action that "holds" the engine at the selected rpm limit without backfires, extreme roughness or engine damage. " and this works on his civic which is fuel injected if im not mistaken the only thing the factory rev limit does is fuel cut. the ecu would probably adjust timing accordingly but not because of the rev limit, but because fuel is being cut. so if you set this to a certain rev limit the ecu would still adjust fuel and timing accordingly. |
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06-20-2004, 02:04 PM | #11 |
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just saying the trurth, i would have no other car other than my subaru at the drag, i love it. but it is hard to have consistant times with a stickshift turbo 4wd car, the 60'times are all over the place. it is nothing new. autos are the best for bracket racing. i only use bracket racing nights as a test and tune with no chance of winning. subarus should stick with racing other similar cars or try heads up classes.
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06-20-2004, 02:05 PM | #12 |
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MSD also has the Launch Control Module Selector that will help control revs on launch as well as top end for between shifts. that could be an option as well.
the UTEC has launch control, just get that and you have your engine management also. |
06-20-2004, 02:07 PM | #13 | |
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06-20-2004, 02:08 PM | #14 |
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ok, maby i am mistaken, so try it, i don't know why, but try it.
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06-20-2004, 02:13 PM | #15 |
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hey, it is tough to drive these cars at a drag. i know. just ask anyone who has draged. ask turbo xs how hard it is to repeat a run at the same time. heat soak, and launch affect this car more than any other. nobody should feel bad if they have problems with launching, there is no other car as hard to launch. period.
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06-20-2004, 02:21 PM | #16 | |
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06-20-2004, 02:22 PM | #17 | |
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06-20-2004, 02:27 PM | #18 | |
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06-20-2004, 02:56 PM | #19 |
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you are no fool. ralax, but a crappy auto does usually win in bracket racing.
can you think of a harder car to launch? i don't know about your trans, maby you are a caring driver and will get lucky. nice car! |
06-20-2004, 05:23 PM | #20 |
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the fact is that bracket racing is more then just getting down the track....thats why I dialed a 13.60 the entire night on friday.....yea, i just ran a 13.33 the run before that in time trials. It's all about playing games and getting good lights. the car I ran 1st round was running 12.20's all day and when he got beside me dialed a 13.30. hmmm....that was a sign that he wanted to play...so i signed up for his game. He went out first round after my .513 light i ended up with 3rd for the night...out of 27 cars...even rental auto's were there.
But anyway... back on track...My main theory behind this was if possible to just use the soft touch and have it activated by a clutch switch. So if i can use the soft touch on the sti then my idea will work. Utec is out of this cars budget for right now, till i get my other money pit done. I just want to make sure first if by adding the soft touch if it will make the car do anything funny. I'm fairly new to this subaru stuff, but i'm just trying to figure out how they work oposed to other cars. So far i didn't hear anything that it will do bad to my car....again, maybe msd will be able to help. |
06-20-2004, 05:42 PM | #21 |
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i was familar with an old unit from msd. the company use to have three or four products. now they can fill an entire book with products. but i think to use their new soft rev limiter, you need to switch to a msd ignition, also need a unit to change tach lead to work with msd products, then buy a third box, the rev limiter.
does not sound cheap to me, maby $1000.00 for all that. forget it. you would be the guinne pig and it may turn out to be a nightmare nothing wrong with stock ignition system. i think it is a good idea to use a rev limiter on launch. do not know if factory computer is ok with it though. |
06-20-2004, 07:47 PM | #22 |
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get a UTEC turboxs.com
it has launch control and a flat shift feature... |
06-20-2004, 09:24 PM | #23 | |
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thanks john, i was worried no one was going to post this. |
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06-20-2004, 09:38 PM | #24 |
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That does answer the question. In a different way then i was looking for. But i guess i will have to contact msd to see if my idea would work. If i have to buy a full msd ignition and all that to even be able to use the soft touch then it is not worth the upgrade and the UTEC would be the way to go. But if i can go with just the soft touch (and no one has factual info stating that it won't work on the sti yet) then for what i want right now....the msd will be good for $100.
But once i find out for sure if just the soft touch will work then i will definately let all of you know. Hopefully I will know tomorrow. I'm not saying that i shouldn't get the UTEC, it's just that right now, my money is not going to this car, sure maybe $100, thats nothing compared to $1200. |
06-20-2004, 10:37 PM | #25 | |
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