Attn Engineers: Modifying subframe for exhuast
Originally Posted by 11SECDWS6
Is there anyway you can move the engine forward a few inches to increase clearance between the tranny and the frame?
Originally Posted by tuske427
...do you have to use the Spohn torque arm?
...what about matching it on both sides?
...what about matching it on both sides?
Originally Posted by MrDude_1
.... why dont you just weld on a Tq arm mount to a "drews style" crossmember, and re-enforce that??
Originally Posted by 11SECDWS6
...we are talking about Joe blow here (no offense) basically redesigning a structural member of a car that GM has spent millions of dollars designing, analyzing, testing, etc.
Could you actually sleep at night knowing that you recommended to someone that they make a modification to their car that could compromise their safety?
Could you actually sleep at night knowing that you recommended to someone that they make a modification to their car that could compromise their safety?
Originally Posted by 11SECDWS6
Would you be willing to suffer the repercussions of a lawsuit if something happened because you said in writing that it would be safe to cut up a subframe? If you could, then your obviously not licensed professional engineer.
Originally Posted by 11SECDWS6
I don't see any point in hacking up a Gen III as it will also likely depreciate the value of the car even futher.
Originally Posted by super_kev
Well, since the car has been modified with a custom cage I built, custom SFCs, and seam welded, doing this isn't going to depreciate the value any further. If I had any plans to sell it in the future, I wouldn't be doing all this work.
how well did that seam welding work out for you?
im going to be under my car anyway when i put the SFCs on... i was thinking about going over some areas... like the subframe to floor points... any tips?
Originally Posted by 02NBMWS6
Your ****** weird man...lol
that "last page viewed" window, isnt exactly the most accurate way to time someone.
especially when they're like me and have multiple sessions (windows) open at a time.
and even more so when the board is spread out over several servers, like LS1tech is..
now im sure brains could make it accurate again, but he has other, more important things to do the board first....
Originally Posted by 11SECDWS6
Nope, but similar to brains I have much more important things to do than argue something so trivial.
You guys try to have a good day....
You guys try to have a good day....
im having a great one. All of you knock it off. Keep this on topic please... 
I haven't driven the car since I've started all this work on it, so I couldn't tell you. Plus I installed the cage and SFCs at the same time. However, I believe it would make a big difference by itself, as the spot welds aren't as strong as a good MIG weld. I welded only the inside of the car from the firewall, along the sides, and the back to the end of the gas tank hump. I will probably be seam welding the subframe area near the firewall before I put the car on the road.
Clean the seams from the oil/tar sealer, and to make an even cleaner weld, grind the primer coating (gray) off before you start. I didn't do the latter until a ways down the road. I was a novice welder a year ago, and even though I had taken welding classes before, it didn't dawn on me that the gray I was seeing was primer and not bare metal. After all, I didn't have any problems getting spark, and at class we used only bare metal that gave spark, so I thought I was good to go.
Now I know what I am doing, and I've gone back and checked my earlier welds to make sure they were ok. If you have more questions regarding seam welding, PM me.
Originally Posted by MrDude_1
how well did that seam welding work out for you? ...any tips?
Clean the seams from the oil/tar sealer, and to make an even cleaner weld, grind the primer coating (gray) off before you start. I didn't do the latter until a ways down the road. I was a novice welder a year ago, and even though I had taken welding classes before, it didn't dawn on me that the gray I was seeing was primer and not bare metal. After all, I didn't have any problems getting spark, and at class we used only bare metal that gave spark, so I thought I was good to go.
Now I know what I am doing, and I've gone back and checked my earlier welds to make sure they were ok. If you have more questions regarding seam welding, PM me. LS1 Tech Stories
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Originally Posted by 11SECDWS6
I have much more important things to do than argue something so trivial.
In the picture "looking rearward" the welds in the background look really good. The way everthing is laid out (as well as how this thread is laid out) it looks like you're going to be successful in getting this issue resolved. It is evident that a lot of care is being put in thus far.
That is one clean-looking third gen from the little bit that I can see.
Ben T.
Last edited by Studytime; Aug 1, 2006 at 04:06 PM.
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From: So.Cal.
Originally Posted by 11SECDWS6
...Yes, it can be done safely. But only if it were done right. I'm not sure that using bags of concrete is a very sound and professional way to do the testing. I would tend to think that a frame tester specifically built for that subframe along with strain gauges placed along the subframe would be the most professional way to do it.
Will it be cost effective? Heck no. I've personally spent hundereds of thousands of dollars (of my employers money) testing various products and I can assure you that one test can easily cost 20k to perform. Its not cheap by any means....
Will it be cost effective? Heck no. I've personally spent hundereds of thousands of dollars (of my employers money) testing various products and I can assure you that one test can easily cost 20k to perform. Its not cheap by any means....
it may not be professional, but if planned out carefully and done in a manner to allow repeatibility/consistency it would be effective and allow the right decisions to be made from the results (making it right)...
lol, us Joe's
don't have a spare $20K or $20M to spend, and if we're going to wait to for that much money to fall into our lap we'd never build anything...! Just because a person doesn't have the money nor the machinery does not mean they can't do it [right/correctly];
and you don't have to be a licensed and/or professional engineer to do something right or to have some sense about it (I'm not dissing you or any LPE's or PE's, I'm just making a statement);
I'd say super_kev has looked at his various options, and cutting/welding his subframes is one of them, and modifying the crossmember is another; he's obviously planned it out, feels confortable about it, showed he has a very good idea how to do it, and understands that loads/stresses have to be dealt with; I believe he'll do a good job of it; I'd love to see his pics when he's done.
(Mr Dude and SStroker, ...interesting digression on relocation bracket/LCA geometry... I'm reading/learning about geometries, wish I had some software to help me visualize suspension motion...)
Last edited by joecar; Aug 1, 2006 at 04:20 PM.
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From: Upstate NY
Originally Posted by 11SECDWS6
Nice way to back-pedal. I appreciate your 55 minute long articulating of your response (I watched you from the public profile window). But I still say that in my opinion, its not worth the effort.
BTW, I'm starting to like the zoomies through the hood. Thanks for the idea.
BTW, I'm starting to like the zoomies through the hood. Thanks for the idea.
LOL! FWIW, I tend to read/respond during lunch break or coffee break time. Every once in a while I take a pause to work. Must be nice to have lots of free time.
Yeah, when I was in the OEM auto business (PC), we spent lots of money on testing rigs, but some folks did extra-curricular vehicle building/modifying and the more arcane methods were used. Results were very similar...within a few %.
FWIW, you can get actual torsional and bending rates as well as comparative rates.
For zoomies, look at truck pull headers. As you know, better performance than 8 stacks.
super-kev, you are definitely NOT a Joe Blow. I'd like to see you car sometime.
Staging Lane
Joined: Jun 2006
Posts: 63
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From: Michigan
I can help with some advice on seam welding if you want. Before I graduated college I worked as a fabricator for the Subaru rally team and part of the shell prep was to seam weld the entire shell. Weld 1 inch long beads about 1 inch to 2 inches apart. Dont put a continuous bead on the seam as it will put too much heat into the shell without adding much in rigidity. The normal practice is to weld a bead in one corner of the car, move to another corner put a bead down, then move to another. This prevents putting too much heat into one local area. In the UK, the WRC cars are welded while bolted down to a jig to prevent them from moving. Afterwards, the suspension points are checked on a CMM. In the US though, we didn't have that luxury, so we made every effort possible to prevent warping the shell.
After seam welding, grind down the welds. Any weld sticking up above the sheet metal adds no rigidity and is dead weight. You can remove about half the weight you added with welds by grinding them flush with the sheet metal.
If this is going to be a track car and you want to strip some of the rubberized undercoating off, there's a nice trick for that as well. We get a bottle of liquid nitrogen. You can pick one up at a welding store that supplies gasses. You'll also need about 6' of the steel hose which they carry as well. Freeze the undercoating for a few seconds, then chip it off with a hammer. You'll be left with pretty sheet metal and a pile of hardened undercoating on the floor that can be easily swept up with a broom. It's quicker, cleaner, and much easier than heating the stuff up with a torch and scrapping.
Al
After seam welding, grind down the welds. Any weld sticking up above the sheet metal adds no rigidity and is dead weight. You can remove about half the weight you added with welds by grinding them flush with the sheet metal.
If this is going to be a track car and you want to strip some of the rubberized undercoating off, there's a nice trick for that as well. We get a bottle of liquid nitrogen. You can pick one up at a welding store that supplies gasses. You'll also need about 6' of the steel hose which they carry as well. Freeze the undercoating for a few seconds, then chip it off with a hammer. You'll be left with pretty sheet metal and a pile of hardened undercoating on the floor that can be easily swept up with a broom. It's quicker, cleaner, and much easier than heating the stuff up with a torch and scrapping.
Al
Originally Posted by ProdriveMS
I can help with some advice on seam welding if you want. Before I graduated college I worked as a fabricator for the Subaru rally team and part of the shell prep was to seam weld the entire shell. Weld 1 inch long beads about 1 inch to 2 inches apart. Dont put a continuous bead on the seam as it will put too much heat into the shell without adding much in rigidity. The normal practice is to weld a bead in one corner of the car, move to another corner put a bead down, then move to another. This prevents putting too much heat into one local area. In the UK, the WRC cars are welded while bolted down to a jig to prevent them from moving. Afterwards, the suspension points are checked on a CMM. In the US though, we didn't have that luxury, so we made every effort possible to prevent warping the shell.
After seam welding, grind down the welds. Any weld sticking up above the sheet metal adds no rigidity and is dead weight. You can remove about half the weight you added with welds by grinding them flush with the sheet metal.
If this is going to be a track car and you want to strip some of the rubberized undercoating off, there's a nice trick for that as well. We get a bottle of liquid nitrogen. You can pick one up at a welding store that supplies gasses. You'll also need about 6' of the steel hose which they carry as well. Freeze the undercoating for a few seconds, then chip it off with a hammer. You'll be left with pretty sheet metal and a pile of hardened undercoating on the floor that can be easily swept up with a broom. It's quicker, cleaner, and much easier than heating the stuff up with a torch and scrapping.
Al
After seam welding, grind down the welds. Any weld sticking up above the sheet metal adds no rigidity and is dead weight. You can remove about half the weight you added with welds by grinding them flush with the sheet metal.
If this is going to be a track car and you want to strip some of the rubberized undercoating off, there's a nice trick for that as well. We get a bottle of liquid nitrogen. You can pick one up at a welding store that supplies gasses. You'll also need about 6' of the steel hose which they carry as well. Freeze the undercoating for a few seconds, then chip it off with a hammer. You'll be left with pretty sheet metal and a pile of hardened undercoating on the floor that can be easily swept up with a broom. It's quicker, cleaner, and much easier than heating the stuff up with a torch and scrapping.
Al
that is a great idea to try with the undercoating.... i think im going to try that... i dont have any nitrogen, or any empty bottles to have it filled... but i do have some nitrous left over.. that sprays nice and cold too... costs more, but i already have it availible....
i need to get that undercoating off to weld on the SFCs.
so just a bunch of 1" long beads.. heh, i can do that.
Interesting topic. Being a former Test Engineer for GM and a Japanese OEM(forgive me) it's easy to see the areas in these vehicles that could use improvement (There's a lot of compromise between groups when developing these cars). thats why there are the abundance of venders making parts to make our car's "better". Many of these after market companies wouldn't know Modal Anaysis from an Finite Elements model, but they make parts we all use. Point being, experienced fabricators can easily achieve stiffer and more robust structures than what is built into them from the factory. On the other hand, a novice could be cutting into a structural member and Jeopardize the integrity of the vehicle being modified. Looks to me like the methods employed above would work well if correctly fab'd and welded. While everyone may not have quality test equipment, basic methods suggested above can be very practical in verifying vehicle stiffness changes.
7 Second Club
Joined: Oct 2006
Posts: 55
Likes: 0
From: Eastern Pa
I had a 3rd gen before my present car, and i did exactlly the same thing, and reinforced the area which i cut out, and i had a 4" exhaust pass thru that area, it wasnt a thru design, like a hole as much as a clearance cut. It will work especially if your suporting the surronding area with sub frame connectors. It worked on my car and i went down to 8.8s at 150. with no twisting of the body. Just a thought.
Thanks for the input, but I will stick to the pass through design that I'm thinking about, as it will be stronger than a notch. However, I will have to wait until summer rolls around before I start working on it. 
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with a notch cut/material removal or a through hole cut:
I would guarantee, that if I modeled the structure in a 3D modeling program (solidworks) and did a FEA (finite element analysis) (cosmoworks) using pressure, force and load, you would see the subframe connectors failing FOS (factor of safety).
My suggestions for rigidness, yes use a through hole cut on the subframe. Then weld a tube (larger then the exhaust pipe) inside the Subframe from side of the cut to the other.
Create a sheetmetal channel (sleave, u-shape etc..), drill matching through holes, through the channel. Then line up the channel over the subframe, aligning the through holes to be concentric and weld. For extra support maybe weld up a gusset between the floor of the car and the subframe and or subframe sleave.
I would guarantee, that if I modeled the structure in a 3D modeling program (solidworks) and did a FEA (finite element analysis) (cosmoworks) using pressure, force and load, you would see the subframe connectors failing FOS (factor of safety).
My suggestions for rigidness, yes use a through hole cut on the subframe. Then weld a tube (larger then the exhaust pipe) inside the Subframe from side of the cut to the other.
Create a sheetmetal channel (sleave, u-shape etc..), drill matching through holes, through the channel. Then line up the channel over the subframe, aligning the through holes to be concentric and weld. For extra support maybe weld up a gusset between the floor of the car and the subframe and or subframe sleave.
i know for a fact that the entire car, stock, fails a modern computer test.
3rdgens were the first GM car to go thru the complete computer design process, with the goal of using the computer to tell them how little they needed...
its not a very strong chassis... for what its made of, its stiff... but its not made of much. lol.
3rdgens were the first GM car to go thru the complete computer design process, with the goal of using the computer to tell them how little they needed...
its not a very strong chassis... for what its made of, its stiff... but its not made of much. lol.
