1g cross member/radiator support necessary?

[Ludachris]

I believe a FWD is different, but on the 1G AWD, you have a brace that runs from tow hook to tow hook under the car, bolting up to the sub frame. That brace has the front motor mount attached to it and has a couple sub frame braces attached to it. It's obviously a critical piece. However, there is also a cross member integrated into the sub frame running parallel to that brace which holds the wiring harness and has the lower radiator mounting tabs attached. It's almost as if it's redundant due to that other brace. On a FWD, it seems the forward running sub frame brace connects to this cross member, but not on a AWD. Here's a photo of the cross member (U-shaped) I'm talking about:

So, what do you think? Can it be safely removed on a car that sees a lot of track time (road course)? Or would it cause some flex issues? I'm planning on replacing the other brace that runs parallel with a tubular version with an integrated motor mount and provisions for the radiator mounts and forward running sub frame braces. I figured if I just used a little thicker bar, it would be strong enough to prevent any flex that might occur from removing the cross member.

Thoughts?

 

[TurboSportAWD]

I would think you would be okay. I would take it out and maybe leave provisions for extra bracing if flexing becomes a problem.

 

[dsmmack]

I removed mine and replaced the whole lower section with a tubular front. Got the idea from Wes Hess (RIP)
I fab'd attachment points for the lower north south bars to bolt onto.

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Have not finished the build yet.

My reason for doing the front bar:

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Extra short route piping. Plus I can tuck the 24x12x4.5 core in there tight up against the car as much as possible. Intercooler end tank will couple up with turbo via just one coupler and then I only have the cold side charge piping.

 

[Ludachris]

Very nice. You ended up combining the two. I think that's exactly what I will do. Just need to start gathering up some materials (and go buy my damn argon bottle already).

Can you give me the specs on the front motor mount you fabbed up? Specifically, the size of the mount for the poly insert... and the poly insert specs. Also, what size tubing did you use for the main bar?

 

[->PrOjEcTGS<-]

Are you trying this to save on weight? Or do you need more space for future goodies?

I would do like dsmmack did. But, to strengthen it more (since you road race) I would add some triagulation in the tubular section to keep the frame rails from flexing up and down independently going in and out of turns.

Sort of like this:

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Then to really make it strong you can add some gussets like this:

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[Ludachris]

More space, strength, and weight reduction - in that order. I would probably do some type of triangulation, but I'd have to account for I/C piping and other pieces.

 

[dsmmack]

Very nice. You ended up combining the two. I think that's exactly what I will do. Just need to start gathering up some materials (and go buy my damn argon bottle already).

Can you give me the specs on the front motor mount you fabbed up? Specifically, the size of the mount for the poly insert... and the poly insert specs. Also, what size tubing did you use for the main bar?

The front motor mount is nothing more than the stock motor mount shell with a 1g Rear solid poly insert that was shaved down thinner to fit into the stock shell. The rear mount insert is wider than the front, and the front aftermarkets are just those damn formed to fit with the stock rubber inserts, Once I shaved down the solid poly mount and fit it in there I bolted the motor mount bracket and the mount to the block and mocked it up in place and then tack welded the round shell to the front crossmember, Pulled the polly back out and then fully welded the shell to the frame

The fab of the bar was easy. Its only just 1-3/4 mild steel cage tubing as that is what I had on hand, Plus I don't have access to a TIG and only have a MIG so the mild steel was the easiest way for me to go. Bent it up with my buddies tube bender. Welded bent 6x6 cage plates onto the frame rails and from there welded the bar up to the plates itself. I think the bar center on center on the legs of the bends was 38 inches wide, If I recall correctly.

I have a build thread over on dsmtalk if you want to view all the pic's from start to finish.
I guess should have been posting this stuff over here as well.

I mostly built this myself for space concerns. I used to run a w2a intercooler setup with the ic above the trans, Had overall 2 feet of charge piping, was such a spoiled bastard with retarded fast spool but wanted to get rid of the clutter of the w2a setup and kept reading great things about this garret fmic core that I wanted as little of charge piping as possible, Everyone is doing top mount turbo setups but you still have all that charge pipe from the outlet to the core. Wanted to remove this extra piping and just go straight from the turbo to the core.

Really it does not remove much weight at all. Its slightly lighter but honestly the rad core section that you remove is all just sheet which weighs nothing. The crossbar for the n/s bars is close to the same weight as the new bar I put in. If you made it from chromoly it would be a bit lighter overall.

Good luck with the build. If you need anything just shoot me a pm or something.

 

[Jeff99GS]

I can understand this helping out with SPACE. But that can't be much lighter weight than the stock support. Unless you use some High strength Aluminum or something.

I know on the 2g this piece only weights about 8-12 lbs max. I guess it could be stronger though!

 

[Ludachris]

With weight reduction, it's not all about cutting massive amounts at one time - I've already done that as much as I can for the most part. It's the combination of several efforts that help cut the weight down... this isn't being done mainly for weight reduction, but it's one of the reasons - read the first sentence of my last post (#6).

Road racers are always looking for ways to shed weight, make things stronger, and create more space for different configuration options. Many times, projects like this don't make sense for a daily driver - this isn't a daily driver.

 

[Jeff99GS]

With weight reduction, it's not all about cutting massive amounts at one time - I've already done that as much as I can for the most part. It's the combination of several efforts that help cut the weight down... this isn't being done mainly for weight reduction, but it's one of the reasons - read the first sentence of my last post (#6).

Road racers are always looking for ways to shed weight, make things stronger, and create more space for different configuration options. Many times, projects like this don't make sense for a daily driver - this isn't a daily driver.

Yeah that makes sense. The space Is definitely a good reason for this mod. However I would like to see a comparison test of the strength/rigidity of the TUBE verses the Square core. I honestly think a round DOM tube would Flex MORE than the square core. Just a theory tho. It would be hard to test it without some serious equipment.
All I know is when I went from a Chrome moly Mountain bike to an aluminum Frame bike I could feel the difference in the rigidity of the frame. The Guy at the Bike shop said that is because Chrome moly/ mild steel can FLEX more than aluminum. I would be curious to see how much flex you would get around a high speed turn with the core cut and replaced.
The whole point of a SQUARE core is that the BENDS and CORNERS in it give the steel added strength. A Square tube is harder to bend than a round one. I used to be a sheet metal worker so I know all about adding cross brakes and bends to metal to ad strength.

I'm not trying to shoot down your Idea, just making sure you consider all the safety/drivability factors before you do this mod. That core is a major part of the cars structure

I guess you could always put on a new core if It didn't work out for you!

Maybe you can try some 7075 Aluminum square stock and bolt it in?

I know when It comes to weight reduction the first thing I think about is my big old beer gut hahaha I could lose 30 or 40 myself ....NOW that is weight reduction!!

 

[Ludachris]

Yeah that makes sense. The space Is definitely a good reason for this mod. However I would like to see a comparison test of the strength/rigidity of the TUBE verses the Square core. I honestly think a round DOM tube would Flex MORE than the square core. Just a theory tho. It would be hard to test it without some serious equipment.
All I know is when I went from a Chrome moly Mountain bike to an aluminum Frame bike I could feel the difference in the rigidity of the frame. The Guy at the Bike shop said that is because Chrome moly/ mild steel can FLEX more than aluminum. I would be curious to see how much flex you would get around a high speed turn with the core cut and replaced.
The whole point of a SQUARE core is that the BENDS and CORNERS in it give the steel added strength. A Square tube is harder to bend than a round one. I used to be a sheet metal worker so I know all about adding cross brakes and bends to metal to ad strength.

I'm not trying to shoot down your Idea, just making sure you consider all the safety/drivability factors before you do this mod. That core is a major part of the cars structure

I guess you could always put on a new core if It didn't work out for you!

Maybe you can try some 7075 Aluminum square stock and bolt it in?

I know when It comes to weight reduction the first thing I think about is my big old beer gut hahaha I could lose 30 or 40 myself ....NOW that is weight reduction!!

If square sheet metal braces like these are generally considered stronger than tubular, I'd have to think you'd see fewer race cars moving to tubular chassis pieces for added strength. The general consensus from what I've found seems to be that replacing factory sheet metal bracing and suspension components with tubular pieces will increase rigidity and save weight in most cases. That's why so many road race DSMers would like to swap out the stock sub frames for tubular replacements (like the Mustang and Camaro guys do) if it weren't so damned expensive to do so. Same goes for suspension pieces.

And usually, in order to use aluminum in place of steel, you have to use larger pieces, which means it might be lighter weight, but you'll be taking up a lot more space than you would with the stock configuration most likely, which is not an option for me.

Trust me, I've thought about it plenty, and I've found a few project car threads that have gone this route - most notably, the AMS Evo X car built for Time Attack. Granted, that car is obviously designed differently than a DSM from the factory, but it's still a decent comparison.

 

[99gst_racer]

I removed it on my 1G, Chris. I did it to remove mass to make more room for unique configurations, as you said. I can tell you that it's not very heavy by itself. Although it sat in the garage for 6 months, I never did get around to weighing it, but it's probably about 4 lbs. It does, however, free up quite a bit of space. Makes it much easier to run a side exit exhaust up front.

This is the best picture that I have that shows that area on my 1G:

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My 1G will be a drag application, not for a road course. But, I feel that removing that section won't amount to less structural support as long as the crossmember is still in place. I plan to weld radiator mounts to the crossmember like dsmmack did, so I had no real reason to leave the radiator support in place.

 

[Ludachris]

Paul, what did you do with the ends of your fabbed cross member? How does it attach to the frame exactly? And what are you doing with the wiring harness that is routed through the piece you removed?

 

[99gst_racer]

Paul, what did you do with the ends of your fabbed cross member? How does it attach to the frame exactly? And what are you doing with the wiring harness that is routed through the piece you removed?

Here is what the ends look like: PIC1 & PIC2

It attaches the same way and in the same location as the factory crossmember.

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I no longer have most of that wiring harness. I've eliminated all unneeded accessory wiring from the car, and that included all but a few of the wires that ran across the front. The remaining wiring will be ran along the firewall instead.

 

[knochgoon24]

I've thought about cutting the section out from across the top of the radiator support and running a 3/8" thick piece of aluminum bar or L across it with custom radiator and A/C condenser mounts. The bar would require hood pins, but I think the latch would work with the L.

I just hate how the A/C condenser and radiator sit so far back in that opening.

 

[Jeff99GS]

If square sheet metal braces like these are generally considered stronger than tubular, I'd have to think you'd see fewer race cars moving to tubular chassis pieces for added strength. The general consensus from what I've found seems to be that replacing factory sheet metal bracing and suspension components with tubular pieces will increase rigidity and save weight in most cases.

Yeah, you are right...otherwise people wouldn't be doing this type of stuff. I guess I would just be leery of removing it completely on a street car. Since yours will be for road racing it will probably be fine.

 

[knochgoon24]

If I were road racing, I'd want something up there.

 

[Slippi84]

Two more pics of Paul's cross member

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[TSimage]

Here's mine:

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