383 replies to this topic

[Rockoz]

What are using for protection where the pipes go through the tinwork?

 

 

Cheers

 

Rob

[Shtstr]

What are using for protection where the pipes go through the tinwork?

Basically a heavy duty rubber grommet.
 
 
Cheers
 
Rob

[Shtstr]

Been doing a bit of research on LS1 engines and they're static and dynamic compression ratios.
From what I can find online the LS1 has a compression ratio of 10.2 to 1 and the inlet cam depending on year model can close anywhere between 43 degrees after bottom dead centre and 87 degrees bottom dead centre.
Obviously this will have a massive effect on the Dynamic compression ratio.
So on a ls1 with factory rods stock stroke and factory cam.
The stactic compression ratio of 10.2 to 1 the cam 87 deg ABDC the dynamic compression ratio is only 6.51 to 1. Very low and explains why they suffer from low torque
Now keeping everything the same but use the factory cam that inlet closes 43 deg ABDC and the dynamic compression ratio jumps
to 9.28 to 1
This cam is found in the ls6 engine.
It produces 405 hp in this form.
It would explain why the ls6 is more powerful over the ls1 engine.
So having said all this I've decided to mix up the internals a bit and come up with my own design build.
The engine is a ls1 with stock stroke but has a higher static compression ratio longer conrod.
With this combination I have achieved a static compression ratio of 12.05 to 1 and more importantly a dynamic compression ratio of 9.35 to 1.

Hopefully it will be enough for what I want.

Edited by Shtstr, 24 December 2020 - 02:58 PM.

[Shiney005]

Is there a formula available online to work all that out?

[Shtstr]

Is there a formula available online to work all that out?

http://www.wallacera.../dynamic-cr.php

[I'm a Red Motor fiend]

The Wallace calculator is a good one and the only one I use.
Said it before and I'll say it again, static comp is just a number that means jack sh_t. Know your dynamic.

[Shtstr]

The Wallace calculator is a good one and the only one I use.
Said it before and I'll say it again, static comp is just a number that means jack sh_t. Know your dynamic.

I know that I'm safe to run upto 9.7 dynamic compression ratio before I to go race fuel or e85.

[Shtstr]

Well started thinking about the headers I had and didn't think they were going to flow enough for the power level I'm after.
Factory hsv avalanche headers only have a 1.5 inch primary pipes.
Not big enough for 650 flywheel hp.
So one more part has to be hand made as these just don't exist for this type of conversion.

So have been doing heaps of research on exhaust manifolds lately.
Have come up with my own design based on the Defilippo headers.
2 inch steam pipe so 1.3/4 inside diameter.
Will flow more than enough for that power level just have to make them in such a tight area that's all.
Here is a drawing of what I have planned out on the drivers side and will try and mimic the same for passengers side.
Have to go around the steering shaft as not enough room for 4 into one on either side of the engine.
Will be 3 into 1. 3 x 2 inch in and 3 inch outlet and then a reducer from 3" to 2.5" to flow into the exhaust system.

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[warrenm]

Why steam pipe? That will make them very heavy.

[Rockoz]

Might be better off going tri y?

Basically 3 2 into 1 joiners each side.

 

Cheers

 

Rob

[Heath]

1-3/4" primaries would probably be the ticket. I don't really understand the inclination towards steam pipe though.

[Shtstr]

Steam pipe bends are a lot tighter than stainless steel mandrel bends.
I know it will be heavy with steam pipe and will require extra brackets to make it less reliant on the header bolts.
But I have very little clearance for any manifolds to fit and clear all obstacles in the way. Engine mounts steering rack and shaft. CV joints and chassis rails.
To give you a better idea of how tight it is in there the factory cast header clear but the pipe that connects from the manifold to the cats has to be squeezed to half it's size due to the torana rails being in the way and also the fact they won't flow enough for the hp.
HSV avalanche headers also had to be squashed by 10mm on the primary pipes and then the secondary was squashed in half again to clear the rails.
So custom headers it is.
The only drawback with steam pipe is the weight.
Other than that it is a lot better for size and flow.

[Shtstr]

This will give you an idea of what I was saying about the radius of the different bends.
Stainless steel bends and steam pipe bends.
You can clearly see the difference between them.
Both are 50mm OD.

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[Shiney005]

Should be nice and quiet too.

[Shtstr]

To give you an idea of how tight it is below is 2 pics one of the 90 deg stainless steel bend and 1 of the 90 deg steam pipe bend hard up against the head.
You can see the stainless just about touching the rail and about 2 inches of clearance on the steam pipe bend in the same position.
Now remember you have to get 4 2 inch pipes to the underside of the car and pass everything in the way. I have also added a photo of the passenger side that has more room than the driver's side so you can see some of the hurdles.

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[Shtstr]

Just racks holding it together at the moment so I can get it right. About 10mm clearance on the outside to the rail and a bit more on the drivers side.

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Edited by Shtstr, 02 February 2021 - 05:38 PM.

[Heath]

Impressively compact. Not jealous of that job.

 

I agree with the radius difference of course (I didn't realise that had driven your choice) although your comparison is not fair, as the stainless bend still has the straight tail on each end, haha. Makes them look a lot bigger again.

[Shtstr]

Impressively compact. Not jealous of that job.
 
I agree with the radius difference of course (I didn't realise that had driven your choice) although your comparison is not fair, as the stainless bend still has the straight tail on each end, haha. Makes them look a lot bigger again.

It's so dam tight it's not funny.
I'm still not sure if it will all work yet as I've only got half way through them.
Run out of bends.
21 x 45 deg and 21 x 90 degree bends down and still need about 20 more 45 deg bends I think haha.
The collectors will hopefully be here by the end of the week.
Not a 5 min job this one.
Last time I made a exhaust manifold it took me 3 days to have it finished.
I think I will be lucky to have these done in a fought night haha.

[Rockoz]

Donuts wouldnt have given you the tighter radius?

 

Cheers

 

Rob

[Shtstr]

Donuts wouldnt have given you the tighter radius?
 
Cheers

No unfortunately.
The 90 deg steam pipe bends I've shown above are long radius bends and the 45deg bends are based on that.
They also have a short radius bend but I'm not a fan of them for flow characteristics.
 
Rob

[Shtstr]

Well had to drop the motor and box out to get access to the next part of the pipes to tack together.
Will have to put it back in to finish them off into the collectors and join into the exhaust system.
I have a little bit more room on the drivers side due to the location of the engine mount over the passenger side that is towards the back of the engine.
It's tighter than a nun's you know what haha.

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[Ice]

Thats doing my head in just looking a it Dave 

[Shtstr]

Thats doing my head in just looking a it Dave 

You should try making it.
I still have to make sure that they are within less than 50mm of each other to work properly too.

[Shtstr]

Had to change the pipe flow for number 3 and tuck it up higher to clear the engine mount better on the passenger side.
Just have to put the whole lot back into the car now and finish tacking them up.
Will have to pull the whole drive line back out once that is done so I can weld them out and clean them all up.
Then back into the car to double check them before I send them off to get ceramic coating done.
Whilst they are gone I can finally finish the gearbox tunnel and start stripping the engine for the rebuild along with prep and paint the engine bay.
What's that bright light I can sort of see haha.
Getting closer by the month haha.

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[Shtstr]

Put the engine and box back into the car to finish them off.
This is how tight it really is.
You can see in the photos.
How they snake around the front tail shaft and go each side of the steering shaft.
Just the last bit to the collectors to do now.

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Edited by Shtstr, 06 February 2021 - 12:54 PM.