Alright guys Im porting(gasket matching) and "polishing" a set of manifolds for my car. I am just unsure how smooth I should get the ID of the runners. Ive read and understand that too smooth will actuallly cause turbulance so i stopped at 120grit. SHould I go any further or stop here?

Also would there be any point in gasket matching the ports from the lim to the block if I cant do the block as well?

Heres some pics of the progress so far(not too interesting)

 

In reference to port matching the LIM to engine mating surface I see there is room for improvement, does anyone know if the gasket is off this much on the block itself? I dont have any spare blocks at this house to check.

 

I could be wrong, but that looks a little excessive. I know on mine it isn't even close to that.

 

How did you go about deciding how much to remove? I laid the gasket over, held it in place w/ bolts and traced the material within the gasket, then grinded that away, hence matching it to the gasket and eliminating any bottleneck effect.

I appreciate your input, I put this here for criticism, do you have any pics of yours?

 

Thats about right for normal gasket matching.

The intake manifold flange is usually a little smaller than the intake ports... this is to allow a bit of a step to prevent reversion, as well as make sure the ports don't face a step in the opposite direction to airflow on the engine. I wouldn't grind it all the way out to the the line if you can't do it to the engine as well, you'll hurt airflow when the flow hits the step on the block.

Most of this is pretty pointless anyway. Its more just something to do to whittle away some free time than to actually make any performance improvement. It takes serious manifold porting to make any difference, and it takes serious engine porting to require any alteration to the manifolds.

Then again, sticking with stock intake manifolds on seriously ported 6-port engine is another waste of time. I was more referring to the 4-port manifolds.

 

Well I have a few sets lying around so i figured Id give it a shot, its as close to free HP as you can get. I am also going to port the TB while Im at it. I think this might help along with the current intake and exhaust. Once these go one its going to the dyno so i can tune the SAFC. Overall Im not dumping money into this car, I just want to see how far I can push my daily driver.

Im gonna go to my other spot tomorrow and compare the block/gasket sizing before I touch the lower.

Also Ive been told by a few people that the air bleeds under the secondary injectors arent really necessary since the air is moving well by 3800rpms, is this true? or should i bite the bullet and spend $60 on 2 tiny pieces of plastic?

 

So is a TB port and polish even worthwhile on a stock engine-ported S4 or is it really just an exercise in aesthetics?

Are perhaps the Pineapple port-sleeve inserts the most worthwhile intake mod after a hi-flow air filter and the secondary throttle-plate removal?

If one is going in to install the port-sleeve inserts, is there anything else really worth doing while you're in there? (Other than perhaps new gaskets...)

 

TB port and polish... not really and point for power purposes. Occasionally helps with wet nitrous when fogger nozzles are placed very close to the TB. The TB is not a restriction on an N/A, by any means. Making one piece of engine breathe better when its not restricting the engine will not help to make any noticable or measurable power difference. We are talking fractions of a hp.

Might want to clean the auxilary port actuators while you are in there. I wouldn't bother with gasket matching if you're not going to do anything to the rest of the runners.

People don't get that when you gasket match on a V8 or the like, you port the entire runner and the intake manifold runners to try to keep a constant size. It helps to keep flow the same between each piston, and helps maintain charge velocity. Simply matching up the intake manifold castings for the first 3" into each runner isn't going to make a lick of difference on a rotary, if you leave the remainder of the runners untouched. It won't help equalize flow, and it certainly won't help make power. The money and time (and time IS money) is far better spent saving for a worthwhile, hp improving mod. The 6-7 hours you can easily spend porting and polishing a TB on a stock manifold N/A could easily be spent picking up some extra hours at your job, which WILL get you more power.

 

Thanks Sean. Precisely the kind of insightful response I was hoping for.

Think I'll spend the 6-7 hours driving. Frome here, that's a trip to Mazda Raceway, Thunderhill, Infineon, Mazfest...

 

Time well spent.
How'd you pick up my first name? old post or something?

 

Scathcart, I completely agree with what your saying about the whole runner needing to be matched to make a big difference, but I dont belive that gasket matching is useless.

While flow in terms of volume will not be changed I believe that a smoother path will allow the air to travel faster which still results in more air. For example if a 30mm runner has airflowing through it at a certain rate then all of a sudden the air smacks into a 27mm runner with a 3mm lip around the edge it will be slowed down without a doubt. Theres nothing forcing an increase in speed so flow will suffer, not to mention the turbulence created by the lip.

Yes of course all of theses effects are very minute on a n/a engine but airflow is still airflow. I am half considering dynoing now and then again after the manifolds just to test them.

 

That would be a waste of money. I can tell you, without a shred of doubt, there would not be a lick of difference. There is more variance between runs anyway that you could never prove the miniscule power gain or loss would have been caused by the gasket matching. Even simply going to the dyno on different days will have a drastic effect on the reading. Back to back runs often vary by 2-5 hp.

Go ahead and try it and think there is a difference. The flowbench says there is absolutely none. (S4 full intake manifolds, before and after simply gasket matching on the 2 manifold gaskets) Tested it a long time ago to make sure I was wasting my time. I don't tend to make statements with such authority without testing them first. The flowbench is an invaluable tool that gives back-to-back repeatable results.

Like I said, try it if you want. I'm telling you, without toughing the rest of the runners, it won't make any difference. If you want to make a noticable effect, look into extrude honing the manifolds. Not cheap, but at least it will actually make an improvement.

 

From this fine article...

http://www.turborx7.com/nitrous.htm

 

Thank you for the input. You have kind of killed my expectations but I appreciate you sharing your knowledge. Regardless I have already matched them and since I plan on changing my injectors, and putting in pineapple sleeves anyway I will just go ahead and put them on along with a TB w/ the secondary plates removed.

All in all this wasnt even a huge investment of time like everyone thinks. I bought a Standard Abrasives head porting kit and used an electric drill, it took me a total of 2 hours to gasket match and smooth out everything. The hardest part was getting rid of the bumps in the LIM.

 

I remember reading something about porting the intake.

Like, you want to go from large to small as you go towards the engine. Constricting the intake slightly increases air velocity. This was on an N/A.

They talked about what happens if you just make the ports near the block bigger, and leave the rest stock. It showed a lower intake velocity entering the block because of the jump in size towards the end of the intake. It also said something about keeping size constant and trying to make curves into a D shape.

It was interesting. If I find it again I will post it.

 

Well the stock intake is designed smaller at the bottom than the rest anyway, I left those unchanged, I just touched up the inside of them a little but left the size alone. Now I am not expecting any difference power wise.

 

If you've got the manifolds off, you can go ahead. I agree its not a huge cost in materials. I am just stating that it really doesn't achieve anything for the future readers so that they don't go ripping apart their manifolds in the hopes it will gain them any power. You already had your manifolds off for the sleeve install, so touching up your runners wasn't any big deal.

The big investment in time I was referring to was porting and polishing the throttle body. That's a good 6-7 hours if you've never done it before.