SVX gravel rally car...surely not? Absolutely... - Page 21

K_Dub · #**301** 04-05-2010, 05:43 PM

Oh baby. That looks nice.

Keep up the great work.

dynomatt · #**302** 04-05-2010, 06:02 PM

Nevin...thanks.

I'm thinking that the size of the circle part dictates how much rotation is required to open the throttles the required 90 degrees.

There's a link to a guy who made a set for a Lexus V8, and there's angles galore...super complicated.

Matt

Nevin · #**303** 04-05-2010, 07:32 PM

Quote:

Originally Posted by dynomatt

Nevin...thanks.

I'm thinking that the size of the circle part dictates how much rotation is required to open the throttles the required 90 degrees.

There's a link to a guy who made a set for a Lexus V8, and there's angles galore...super complicated.

Matt

That's true about the size of the circle. You need to figure out how much travel the throttle cable has from 0% throttle to WOT and then apply that to the circle, giving it the same range of motion.

dynomatt · #**304** 04-05-2010, 07:42 PM

Plan b...dual throttle cables has been suggested by somebody else.

Turns out some motorbikes and snowmobiles use dual cables.

Will be investigating that as it would make all of my other problems go away.

M

svxistentialist · #**305** 04-06-2010, 01:12 AM

Bikes do use dual cables all right.

One cable opens the throttles and the other cable closes them.

Joe

TomsSVX · #**306** 04-06-2010, 04:59 AM

Quote:

Originally Posted by svxistentialist

Bikes do use dual cables all right.

One cable opens the throttles and the other cable closes them.

Joe

yes.....

Tom

rallyingrob · #**307** 04-06-2010, 09:07 AM

it doesnt necessarily have to be a perfect circle...

n. american gm products had (have?) lobe-shaped linkages....this provides a non-linear throttle response

GM did this to make customers think their vehicles had more punch/torque/"snap" at the bottom end when they tipped into the throttle

this was fine (i guess) until proper fuel injection came out...the un-natural throttle response yielded tricky 4x4' ing moments in bad situations as well as needlessly barked tires when the light turned green etc...

anyway...

the point is, you can achieve VERY fast throttle opening rates using a non-circular disc device!

i wonder if their is a way to mount it mid-block, (between cyl. 3 and 4) as opposed to being at one end?
it just seems to me that it may impart some un-wanted movement (or accelerated wear) on the linkage if it's pulling from one end...?
or...the #1 and 2 cylinders may not truly open 100% full once the system starts to bed-in with a bit of wear...?

keep up the good work!!

toooo freakin sexy !!

another thought...

can the linkage actuators on the throttle shafts be moved?
or are they keyed to the ends of the shafts?

if they can be between throttle bodies, you could use the 3 centre top case bolts to mount a bent to shape flat metal bracket (gusseted as/where needed) and thus easily mount the rotational device mid-block...
you could use that as your primary and still install one at the end as depicted with a spare cable already installed in-situ for the (unlikely, but never say never!!) time when the linkage/cable in use fails mid-event....

i've always incorporated redundant systems where practical/reasonable...ie: run a clutch or throttle cable alongside the one in use...that way its easy to switch over if necessary...

same thing with ignition systems (ignitor boxes/controllers/ coils etc) and electric fuel pumps too (when possible)

dynomatt · #**308** 04-11-2010, 11:52 PM

Thanks Rob,

Redundancy is key for sure. Spoke to a few people about the cable setup, and with stretch etc...it's probably not the best setup.

I think I'll revert to a linkage. Will probably go for common shaft across the case, with drop linkages to each block...assuming I can get that to work.

Although, this would also work

http://www.perth-wrx.com/vb/showthread.php?p=372756

dynomatt · #**309** 04-12-2010, 12:22 AM

ON another note...car moved under its own power last night...off to the shop this morning to make some custom headers. 36" primaries I'm thinking.

Working on the ITB linkage setup tonight.

Matt

rallyingrob · #**310** 04-12-2010, 06:46 AM

i can picture it now...sexy little gold anodized heim ends etc....subey blue rods...
verrrrrrrrrrrry sexy !!

a friend of mine had a volvo twin carb that he stuffed into a ditch arsing around...

rod type throttle linkage ended up embedded in the firewall and pinned the throttle wide open...by the time he came to his senses enough and shut off the key, the damage was done....engine was toast!

what about hydraulic?

i've never seen one in person, but i've heard of them....would that work?

methinks the return spring on a hydraulic throttle would be hugely stiff!!

oab_au · #**311** 04-13-2010, 08:10 PM

I was thinking that it would be easy to set up if there was a central shaft, running, front to back, in the centre. If you can imagine the standard throttle shaft taken out of the throttle bodies, rotated 90* CW, so that the throttle cable connected from the right rear. The shaft is supported, with two levers on it. The front lever lines up with No 5, and the rear lever, lines up with No 6. The shaft could retain all the std springs and levers for the cable, and you could mount the Throttle Position sensor on the front end.

I can’t see from the pics, how the throttle plates are facing, but it would be best to have the low side of the plate facing the injectors, to help small throttle openings to atomise well.

So if they were set up like that, with the TB levers pointing down, they can be opened with two pull rods down to the shaft. For the No 5, the shaft lever at the front, would point down, and for the No 6 at the rear of the shaft would point up.

What do you reckon?

Harvey.

dynomatt · #**312** 04-13-2010, 09:32 PM

thanks Harvey,

I like how you're thinking.

However...on another forum I'm on, people have pointed out links to guys with VW's and old school porsche's who say that a central pivot, or rod, will be affected by crankcase expansion. Which in turn affects tuning and performance over the temperature range of the engine.

Hence the way I'm leaning is towards the Gene Berg version...or similar to the extrudabody porsche ones which have a rod going from bank to bank, with drop linkages to each shaft. Controlled by a single throttle cable.

I've got my next rally on the 8th of May...I'm worried that I'm running out of time to get it sorted by then.

Matt

dynomatt · #**313** 04-27-2010, 04:19 AM

So I won't get the ITB's on for the rally.

But everything else is on its way.

Got some equal length headers made. Now need a slightly different tune in the megasquirt, modify the sump guard, some registration and we're away.

I'm also trying the 45mm radiator bottom inlet in an effort to fix the cooling issues.

Rally is on the 8th of May.

Matt

dynomatt · #**314** 05-06-2010, 02:06 AM

Here's a bit of a teaser

And a mixture run...way rich.

dynomatt · #**315** 05-06-2010, 04:32 PM

More than 14 hours and no comments.

You guys are either way too hard to please, or have lost interest.

Either way...tomorrow's shaping up to be a great event.

The car feels strong...very strong. Not sure if my butt dyno needs recalibrating, but driving it last night in the cool air, and gee it went hard and sounded fantastic. Harder than I'm sure it's gone before.

This is just with headers too...can't wait to get my heads and ITB's on because that should step it up a few notches.

Here's hoping I stay cool tomorrow...if I do, then it's on.

M