308 Engine Rebuild & CIS to TWM Throttle Bodies Conversion Thread!

No you dont, cam selection combined with compression ratio is what determines fuel requirements. You can run 12:1 static if you run a cam with enough duration to cut your dynamic compression ratio down into the 8's. Lower compression, less duration keeping the dynamic or usable ratio near 8 is what matters. 8.8:1 with P6 cams equals a dynamic comprssion ratio probably in the 7's or lower which means you cant pull a sick whore off a toilet with that combo..

 

Just to clarify, if you take into consideration when the intake valve closes after BDC by using a degree wheel, you can then measure the piston position in the bore, calculate volume and then figure out your usable compression ratio. Because the valve doesnt close at BDC the entire cylinder volume isnt available to compress the charge, what that new ratio is matters and determines the engine's bottom end grunt as well as its fuel requirements for the most part.

 

Another example. My boxer has CIS so I have cam limitations. Taking into consideration the maximum cam duration and overlap the CIS will like will determine the compression ratio I can run and still use pump gas. Its all about the combo. If I ran 12:1 pistons in my car with a CIS friendly cam grind, the car would need more than the available 94 sunoco gold at the pump which is not the path I wish to go.

 

I can't tell for sure from the picture, does the scuffing extend thru the ring area & up to the piston's top, or does it stop with the oil (bottom) ring? Do the rings show signs of scuffing as well?

Are there corresponding scuff marks on the cyl. sleeve?

Here's a link to an excellent tutorial on causes of piston damage including scuffing:
http://www.mlcmotorfactors.co.uk/Trouble%20Tracers/PistonTT.pdf

 

Hey Chris,

Not going to PM you...I'm going to use this as a good excuse to call you up.

Henry

 

Your stock CIS pump will be prenty fine. Nothing at all to worry about.

 

Pizzaman,
Not a problem, the 308 CIS fuel pump mounts down below the fuel tanks. It also deliveres plenty of pressure & fuel flow.

The TEK 3r is a nice system. But it's Electromotive, not Haltech so I won't be able to help you much with it. If you go that way, who do you have lined up to generate maps & fine tune your system?

 

Yes, it's all fine as is.

 

Pretty much. You won't really need the fuel accumulator, so it could be bypassed & removed, but it won't hurt if you leave it in there.

I can help you with Cohline fittings & fuel lines to hook the existing lines to your fuel pressure regulator & rails.

What I was trying to say about Haltech vs Motech is that I know how much effort it takes to learn a specific engine management system, it's software, & how it interacts with an engine. I have no choice but to spend the time to learn the Haltech system in depth in order to do my car. I could then help you if you went with a similar Haltech system as we discussed a year or so ago. However, reality is I just won't be able to committ a similar amount of time to learn the Motech in order to help you.

 

Many 12 cylinder cars like the 400i come equipped with 2 fuel pumps. Two alternators as well but that's another story.

 

The stock pump will handle about 400hp and you are going to make about 270 so stop worrying already, the stock pump is more than fine for your application.

 

The Bosch CIS fuel pump operates at ~5 bar (73 psi). If you are just doing a normally aspirated EFI conversion, you'd actually be better off going to a 3 bar (43 psi) fuel pump as this uses less current and wastes less energy (this is why Motronic fuel pumps don't frazzle the electrical connections like Jetronic fuel pumps ), but no harm using the CIS pump (and a regulator, if necessary) -- and it seems ideal for a boosted EFI application.

 

sealant for both places. I like permatex 518 or similar but there are plenty of things that work well, the factory used silicone.

 

Both of those locations are high precision fits, hence only sealant as mk e says.

Also only sealant between the bell housing & the spacer, & between the spacer & the block.

Lately I've also just been using silicone sealant on the sump covers as they're also well machined.

I prefer the Permatex 515 or 518 as it doesn't set or skim over while you're working the way silicone does.

A little goes a long way here as it ends up an extremely thin joint. Use a bead about 2mm in diameter.

 

+1 for the loktite/permatex 518 anerobic goop