extrude hone - The Unofficial BMW M5 Messageboard (m5board.com)

racer_xbr · 23rd May 2002, 18:06

any one has tryied extrude hone on the intake colector of the v12 engine ?

dinan ofer this for 2000 us and promisses 38 hp ...

regards

MikeC · 24th May 2002, 08:06

38hp seems to be a lot. If that number is true I will have it done at once and ask myself why BMW didn't do it.

Maybe they did it on the S70. I don't know.

...Mike

SteveC · 24th May 2002, 13:02

Extrude honing is worth about 13 HP at the rear wheels on an 850CSi. When Jim Conforti did his E31 dyno session in Atlanta a few years ago, two 850CSi's were dyno'ed; one with EH intakes, and one bone stock. Everything else between the cars was identical. The EH equipped car pulled higher HP and torque figures throughout most of the RPM band and the consensus was that the improvement was totally attributable to the EH intakes.

BTW, do NOT pay Dinan for extrude honing. You can send your intakes directly to Extrude Hone Corp. and have them done for $800. Granted, Dinan powder coats them black, but if you like that look, you can have locally much cheaper than what Dinan is charging.

CarlT · 24th May 2002, 23:31

Hi Steve

Good to see you here. For those of you who don't now Steve, he is a savant in the 8 series world, especially on the CSis

13 hp from extrude honing... Did the owner have a before and after of the engine? I know that BMW engines do differ quite a bit stock. The E39 M5 can vary 30hp...

I just think 13hp sounds a lot, but maybe not. I'm sure to stock 850CSi could differ 10-15 hp, that is only a 2% margin. That said, I'm a believer in honing and ceramic coating.

Carl

MikeC · 25th May 2002, 00:25

Hmm, what exactly does honing and/or coating change? The amount of air, its distribution or just the airflow?

Doesn't the procedure imply new intake manifold gaskets as well (because of manifold removal)?

...Mike

SteveC · 25th May 2002, 01:04

The extrude honing process involves the forced injection and passage of an abrasive sludge through the passages of the intake manifolds. EH estimates the result is an increase in airflow of 3% or more.

When we did the dyno runs, my former 850CSi was the one with the extrude honed intakes, the other was a "stock" 850CSi. I did have a "pre" dyno run, but unfortunately it was from a different dyno, so there was really an apples to apples comparison. We felt very confident that the measured gains were attributable to the EH'd intakes, and not production variations in the engine. Even in just driving them around, the EH car felt stronger.

And speaking of ceramic coating, I just got back my RD headers with their fresh Jet Hot coating. Hope to get them on within the next month or so.

SteveC · 25th May 2002, 01:07

Forgot to mention - yes, to do it right, the slightly enlarged openings on the intake runners should be matched to the intake gaskets, which need some transitioning in. Same for the headers.

MikeC · 26th May 2002, 07:53

I'm curious now, does removing the intake manifolds always require new gaskets?

...Mike

raymondw · 26th May 2002, 10:11

MikeS,

Yes, you don't want air leaks between the cylinderhead and the gaskets.

The gasket's themselves are rather cheap so why take the risk of using old gaskets.

Rgrds,

Raymond

SteveC · 26th May 2002, 13:55

There are two schools of thought on this. One says always replace them because they tend to eventually shrink with prolonged exposure to heat. The other school says that if they are visually okay, then they can be reused by applying a coat of hylomar to both sides. I also recommend using the hylomar even when you're installing new ones.

Jim Wald · 12th August 2002, 09:25

Quote:

Originally posted by SteveC
There are two schools of thought on this. One says always replace them because they tend to eventually shrink with prolonged exposure to heat. The other school says that if they are visually okay, then they can be reused by applying a coat of hylomar to both sides. I also recommend using the hylomar even when you're installing new ones.

I just had Extrude Hone do the intake manifolds for my CSi. The Manifolds are now being polished on the outside on the non-black surfaces, so I can't tell you what the effect on the is until I get them back and the car is together again. However, I can tell you that Extrude Hone quoted me a 20-30 HP gain. Of course, none of these guys quote HP gains at the rear wheels, including BMW's quotes for stock engine output. But Extrude Hone's HP increase quote was for "Stage One". I did "Stage II", where you send them a new set of manifold blocks and they match Hone them too. So, although my car only has 11,000 miles on it, it will be getting new blocks/gaskets, to match the very smooth interior of the intake manifolds. They only sharge $80 extra for the Stage II.