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Discussion Starter · #1 ·
I'm a noob - excuse my improprieties, if any

I have an '84 Supra MKII - engine has good power at low RPM but really sucks at high RPM ( I get blown away by just about anyone who tries! )

I know it's NOT
-clogged catalytic converter
-timing
-in need of a tune-up

Other info
-plugs are all new, nice and golden brown, no fouling
-everything is stock

Any suggestions as to where to start looking ???

Thanks
 

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my car wasn't as strong at high rpms until i put a new cone filter and did a little exhaust work to allow it to breath better. it could need fuel, chek the injectors, filter, pump, etc. maybe your ignition system can't keepp up with the load required at higher rpms?
i'm not an expert but i'd chek these things either way.
 

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i think the exhaust has to do with it. i had a little power at high rpms until i accidently bumped my muffler into something ont he ground and the power wwas just gone. i still have to replace my muffler
 

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Discussion Starter · #4 ·
OK one thing I didn't mention - the fan was really loud. Turns out that my fan clutch was seized - engine had a tough time at 5000+ RPM turning the honking huge fan. Someone replaced the original fan with what seems like a bigger one - the fan shroud is all busted out.

I just removed the fan and fan clutch and the car runs like a scalded cat. No problem with overheating and with a nice cold Canadian winter coming up, I doubt I have to worry about the fan until spring
 

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you'll probably be ok unless you do some long steep hills. Just get another oem clutch fan and you'll be ok
 

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Also I'm not sure what kind of cars youre used to driving but the 5M is a 2 valve per cylinder engine so its not going to pull well at high rpms.
 

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Redline?

SupraWes said:
Also I'm not sure what kind of cars youre used to driving but the 5M is a 2 valve per cylinder engine so its not going to pull well at high rpms.
Whats the recommended redline point on a stock 5 mge? Not even 6K?
It appears 63-6400rpm's on the rpm gauge :?
 

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6k is pushing it...the farthest i push my engine is 5 MAYBE 5500. redline doesnt neccessarily mean thats where u change gears, redlines means ur pushing ur engine and be careful. now unless u got ur engine fixed up, its a different story. at high rpms u experience valve float so ull start to lose power at higher rpms. as always, a gear only takes u so far...
 

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peak power in a stock 5m is some where around 5500 there isn't really a point to push it farther unless you like to...lol, i've never hit the red line but been over 6 many times....
 

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peak power in a stock 5m is some where around 5500 there isn't really a point to push it farther unless you like to...lol, i've never hit the red line but been over 6 many times....
U want max torque (= max acceleration) at the rear wheels NOT max
engine power. u always get more torque at wheels in a lower gear.
so in NA 5/6mg u should shift around 6200 to 6300 rpm (so u don't exceed redline) for max torque over widest rpm range.

for esample: 3rd gear ratio is 25% less than forth gear ratio so engine
torque would have to fall 25% from max before u'd develop more wheel torque in 4th than in 3rd. iirc engine torque at 6300 is only down about
10% from max torque which justifies stayingin 3rd till 6300.
 

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PEAK, REDLINE, SHIFTPOINT

It :shock: looks like the peak of the 5mge is reached @53-5700rpm's.
Redline point is right at 6,400 :?:
And for max accelleration, 62-6,300rpm's is when the shift light should go off :?:

OK, maybe just needing a little bit of tuning,the loosing peak after 5k rpm's makes sense, maybe free up the intake, exhaust , afm and a nice tune up should up the peak enough to where its fine tuned :flex:
 

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Another thing to remember is that a properly set up tranny/rear combo set for max performance will have you come into the gear right around when the motor is making 80% of the torque that it will develope when you shift out of the previous gear at peak HP. (i.e. Your motor makes peak hp at 5800 rpm's, peak torque is at 4700 rpms, and it makes 80% of its peak at 4200... You shift out of the top of 2nd at 5800 rpms and you should be into the bottom of 3rd at around 4200 rpms)

As for the gaining of top end power on a 5M? breathing mods. Filter, intake pipe, header and exhaust. The 5M makes good power down low, but its pretty restricted to breath well at higher rpms. Just a cone filter (or depaneling the stock airbox) alone should have you making power for another 500 rpms passed where you felt it drop off before.
 

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valve float...never thought of that being why my 5m pulls awesome to 5200 but after that it sux. i've taken a 5m to 6750 once and almost got it there again in second at wot. it was interesting. i had a shitty beatup old cressida once i beat the hell outta. got it to 6750 in first after hearing definate rod knock and tried to get it to 6750 in 2nd but only got it to 6700 before it threw two rods not just one and since it was at such high rpms when the connecting rod broke the pistons slammed into the head and shattered it and the crankshaft stopping so suddenly bent the block and twisted the crank and cracked it. it as some fun shit tho! and a huge mess of oil and coolant.
 

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DKJones96 said:
valve float...never thought of that being why my 5m pulls awesome to 5200 but after that it sux..
On the dirt track cars we run here(all small block chevys) we check valve springs at least twice a season. When you lose seat pressure you will lose the top end for sure. I have seen valve springs make more difference than a new cam in some cases.
 

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theres a shift light? lol, my car doesnt have that...or did 85 ptype supras never come with it? maybe my light is broked
 

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OH NO

KesekiSupra said:
theres a shift light? lol, my car doesnt have that...or did 85 ptype supras never come with it? maybe my light is broked
OH NO, my bad, I was saying If you had one of those TACH shift lights like the ones the AUTOMETER rpm Tachs have like the COBALT and AMBER shift lights you can set at whatever rpm's you want them to go off at. Or go on and light up actually :eek:nfire:

Some even have instant playback of your RPM pattern :) I dream of those things sometimes, especially the COBALT setup for my AE101. http://www.madtachs.com/products/cobalt/5in_tach.html

Wanted to know where the aftermarket tach shift light should be set at for street and drag :3gears: :mk2: THINKIN 5,200 - 6,300 RPMS depending on setup :?
 

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only ppl who dont know how to drive need a light to tell them when to shift :p
 

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Speedway sells a add on tach memory module, have one on my firebird, don't know if it is adaptable to supra tach
 
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