914RS4 Tube Chassis 996 Suspension Audi 2.7TT Stage 3, ADDED RECAROS Options

[Curbandgutter]

I'm not sure if the Gurney bubble would take away from the lines of the 914. But yes it is a solution. However I think that with my coil overs and some machining I may not need the bubbles.

[csdilligaf]

this is what a Gurney bubble looks like in that location.

[Curbandgutter]

I see, pun intended. Not feeling it though. I wonder what suspension that car has that it would need that??

[Curbandgutter]

So I've been thinking and came to the preliminary hunch/suspicion that I can't just cut the strut tower height without changing the instantaneous roll center. This would be horrible and would affect the dynamics of the car. I'm going to do some calculations and figure it out. However I'm thinking that I may be confined to keeping the struts whee I have them now and then figure out how to implement it into the car. Anybody have some input????

[FL000]

Isn't the instantaneous roll center determined by the upper and lower control arm geometry? If that is the case I would think strut tower height is independent of it.

[Curbandgutter]

I believe that with the Mc Pherson struts you don't have an upper wishbone. The top of the strut tower is considered the upper wishbone location then you hold a right angle at that location and intersect it with the angle of the lower "a" arm.

see this article

https://balancemotorsport.co.uk/suspension-geometry

It appears that as I lower the strut tower it will raise my roll center. This may not be a bad thing, since depending on where the cg is, it may create a smaller moment arm between the roll center and the center of gravity. If this is the case the car will have less lean in the front end. That may help with creating less understeer. I have to think it through. I have to calc what my cg is up front and then what the 996 roll center is and then what the roll center will be if I lower the strut tower elevation. I need to do some calculations before I make a decision.

[csdilligaf]

I think shortening the length of the strut along its axis will have much less effect than the article shows when the car is simply lowered. By lowering the car the wishbone angle is changed thus effecting the Roll Center. It does not change all that much if you shorten the strut a few inches with out changing the Steering axis inclination. It will change the Instantaneous Center(virtual Point) and I think the rest would still be the same? But I do not have any strut calculation engine so it is just my gut feeling. I just think it has to end up better than the guys who take a 996 and slam it. It will be interesting to see what your calculations come up with.

[Curbandgutter]

Shortening the strut will be a step in the positive direction as is will raise the IRC approximately 5/8". Good (IMG:style_emoticons/default/cheer.gif) (IMG:style_emoticons/default/cheer.gif) (IMG:style_emoticons/default/cheer.gif) I wasn't feeling those Gurney bubbles at all.

[sixnotfour]

Shortening the strut will be a step in the positive direction as is will raise the IRC approximately 5/8". Good (IMG:style_emoticons/default/cheer.gif) (IMG:style_emoticons/default/cheer.gif) (IMG:style_emoticons/default/cheer.gif) I wasn't feeling those Gurney bubbles at all.

your smoker started it.... keep up the build (IMG:style_emoticons/default/popcorn[1].gif)

[Curbandgutter]

(IMG:style_emoticons/default/av-943.gif) (IMG:style_emoticons/default/av-943.gif) (IMG:style_emoticons/default/av-943.gif) You're looking right at the solution gurney bubble.....smoker (IMG:style_emoticons/default/lol-2.gif) (IMG:style_emoticons/default/lol-2.gif) just got it.

[Curbandgutter]

Little update, should be able to finish tying in the front struts to the tube chassis. A couple of progress pics.

Here is the strut attachment point cut down to size. I had to move the tower out and forward to account for the strut inclination angle both sideways and forward and backward.

Here is the octagonal shape that I will be using to box int he strut tower

Here is the "strut brace"

[Curbandgutter]

Forgot to add this mock up. Test fit of parts before tacking them in. Don't worry the tubes will line up.

[csdilligaf]

You know one thing I would like to plan on is moving the driver over a little so you can square up with the pedals. You already are making your own center console box so its a no brainer at this point. The front end progress looks good. Its a big undertaking for sure but your doing an impressive job. Keep it up

[Curbandgutter]

The weather let up a bit and I was able to sneak in some hours into tying the strut towers in. By the way I am really giving it some heavy consideration into changing engines. I'm leaning to a Audi RS4 Stage 3 motor. It will produce 600 HP so its where I want to be. What do you guys think about that motor choice.

[Curbandgutter]

The weather let up a bit and I was able to sneak in some hours into tying the strut towers in. By the way I am really giving it some heavy consideration into changing engines. I'm leaning to a Audi RS4 Stage 3 motor. It will produce 600 HP so its where I want to be. What do you guys think about that motor choice.

[tygaboy]

A short passage from a book I think I'll write about Rudy:

"It will produce 600 HP so its where I want to be." He said this casually, as though this level of power was commonplace, even easily attained or available without much planning. He was, as everyone already knew, power hungry. He would come to look at his initial 600hp as "a decent starting point". Eventually, he printed t-shirts with this slogan on the front pocket:

If more is good then too much is just enough!

On the back was printed "I'd rather be sideways".


_________________________


Rudy - I vote "Go for it!"
Your build is looking awesome.

[Cracker]

You asked Rudy... (IMG:style_emoticons/default/shades.gif)

I am not a fan of the Audi 4.2 RS4 engine...I saw a nice conversion done into a Boxster race car - very underwhelming. It is low on torque and wasn't competitive either...honestly, I don't care for the sound too. There is a high-price to pay when squeezing big power out of small displacement motors - I know all about them, first hand. Synonymous with hand-grenade.

Remember, you asked!

T

PS: Although both heavy and large - I've thought the GTR TT v-6 would be a nice addition to the 914. Audi have already been done...

PS #2: I'm digging your progress - great job!

[Andyrew]

4.2 tt rs4 motor? Thats a lot of weight to make that much power.

Its a compact and complicated setup but 600hp is easily made on that setup and it should be extremely torquey.

I think if It were me it would either be the rs4 NA v8 or a S8 4.2 motor for about 360hp to be more economical.

If I wanted to go turbos again with an auto motor I would go 2.7 built with gt28 turbos or KO4 hybrid turbos. That would put a power range from 325-800hp.

[csdilligaf]

Andyrew, I think you nailed it with the Audi 2.7TT.

[jd74914]

Nice strut towers Rudy! They look like really stiff nodes! (IMG:style_emoticons/default/smile.gif)

The Audi 2.7TT might be a good motor if you want to keep it German. Otherwise a Subaru EG33 or EZ30R with some turbos might work well too-and they'd help lower your CG to boot.

Why are you thinking of moving away from the Coyote? AFAIK they are pretty robust motors to ~650hp (forced induction).