Savage tuning part 3!

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Dre - 17 Oct 2005 03:12 GMT

Okay, so filled the old girl up to the seam in the fuel tank and had another
go and tuning it. I did a bloody good job of completely messing up the
tuning last time so it was a bit hard to keep running, but after some
serious tweaking (90deg turns on the HSN *and* LSN!) I managed to get it
back to some sort of state. I then hit it with an infrared temp guage and
it was reading 90deg C, so lean the HSN out and adjust bottom end.

I managed to get it to the point where I was getting around 120deg C
(115-125deg C range) with fuel in the tank from the seam all the way to bone
dry (stalling out due to no more fuel in fact). I didn't get a chance to
test with a full tank but thats next.

I also think I found the problem, this engine simply doesn't sound like
others I have exprience with and this was throwing my tuning out (I really
shouldn't tune stuff by ear anymore, there are much better *digital* tools
available :) and also the fact that 2nd gear was set waaaaaay to low and
hence I never saw 1st. 3rd gear was also set too high as I only hit it a
couple of times when the truck got air-borne at speed (grin).

Last night I pulled the gearbox out and turned 2nd gear in 90deg and 3rd
gear out 90deg, see how that goes to start with, if that makes the gear
changes more in line with what I want *and* the truck behaves fuel mix wise,
I've nearly got the formula down.

I have no idea how many turns I have adjusted the thing now though, but what
I do know is that the LSN isn't flush anymore, its about 0.5mm in from
flush.

The truck positivily hammers now though, and that with only 1 gear so far
(2nd), so I'm very excited to see how it goes with 3!!!

Cheers Dre

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nospam@noway.com - 17 Oct 2005 06:27 GMT

> Okay, so filled the old girl up to the seam in the fuel tank and had
> another
[quoted text clipped - 32 lines]
>
> Cheers Dre

A tip on the three speed: tighten the 3rd gear clutch all the way IN till
it's tight. This will ensure that 3rd gear will not engage. Now you can
concentrate on the 1-2 shift (real bugger having to yank the tranny to
adjust it isn't it!). After you have 1-2 perfect back off 3rd a turn at a
time till you get all three gears and then fine tune from there.

I went thru HELL tuning my 3-speed as the factory had it set so it would
jump from 1st to 3rd and completely miss second. Not knowing this, I was
going the wrong way on the wrong clutch and it took me forever and a day to
get it right. Elininating 3rd gear altogether solved this issue and made it
possible for me to figure out what was going wrong and get it tuned
correctly. If you call HPI they'll give you the stock settings for the
3-speed with the 4.6 motor. That should get you pretty darn close, assuming
you have stock spur/clutchbell ratio and stock-height tires.

Ran 4 tanks thru the ol' girl today and same rock-solid performance I've had
the past few runs. Looks like the uniflow mod was causing more problems
than it was solving. It eliminated the 1/2 tank lean, but gave her a nasty
un-tune-outable low-end bog and made her REALLY finnicky per way of holding
a consistent tune. Last three times I've run her I've only had to move the
HSN 1/8 of a turn in either direction to get her running right.

Per way of temps, you're lookin' good and can lean HSN further. You're
running 260'ish and can lean her until you get into the 280-290 degree range
(138-143 Celsius) safely. With uniflow mine seemed to run best around
240-250 (118 celsius), but without uniflow she likes it around 280-290
(140). I think most folks are out to lunch on temps, saying 300* is
"overheated" and that 280-290 is "overheating". In my experience, just
about every motor I've ever tuned runs best between 280-300*. Hell, my
buddy's T-Maxx with a Wasp .18 in it runs 300-340 every time he runs it,
smokes like a freight train and 3 gallons later no compression loss and
still running like a sonofabitch.

HTH,

Doc

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Dre - 17 Oct 2005 06:53 GMT

> > Okay, so filled the old girl up to the seam in the fuel tank and had
> > another

<snip>

> > Cheers Dre
>
[quoted text clipped - 3 lines]
> adjust it isn't it!). After you have 1-2 perfect back off 3rd a turn at a
> time till you get all three gears and then fine tune from there.

Yeah I know, you mentioned this allready and I would have followed it if I
didn't have any idea where they were shifting. Since I knew when mine were
shifting I had something to go by (still, I could eat these words when I
find out thats its even worse tonight :)

> I went thru HELL tuning my 3-speed as the factory had it set so it would
> jump from 1st to 3rd and completely miss second. Not knowing this, I was
[quoted text clipped - 4 lines]
> 3-speed with the 4.6 motor. That should get you pretty darn close, assuming
> you have stock spur/clutchbell ratio and stock-height tires.

RR spur/bell so no go there :) PITA spending an hour just to turn *one*
bloody grub screw 90 bloody degrees! However, it looks awesome looking at a
Savage complete with one of its chassis plates removed :)

> Ran 4 tanks thru the ol' girl today and same rock-solid performance I've had
> the past few runs. Looks like the uniflow mod was causing more problems
> than it was solving. It eliminated the 1/2 tank lean, but gave her a nasty
> un-tune-outable low-end bog and made her REALLY finnicky per way of holding
> a consistent tune. Last three times I've run her I've only had to move the
> HSN 1/8 of a turn in either direction to get her running right.

Okay, I dont run the uniflow mod and have experienced only slight lean out
at the end of the tank, however tonight will tell more, going to take it out
for another run, especially since you say:

> Per way of temps, you're lookin' good and can lean HSN further. You're
> running 260'ish and can lean her until you get into the 280-290 degree range
[quoted text clipped - 10 lines]
>
> Doc

EXCELLENT! If I can run the temps up to 140dd I'd get more revs. I found
that when it got to 140 it was SCREAMING, but thought 120 was more the go so
dropped it back (at the expense of a little performance).

Right, leaner on the HSN it is! <evil grin> 340, thats around 165 isn't
it??? DAMN! but if it loves it, who cares. My old T-maxx used to run
around the 150's (C) and Traxxas themselves say that their engines run
hotter...

Thanks for the info!

Cheers Dre

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Model Forum / Radio Controlled / Land Models / October 2005

Savage tuning part 3!