Gregg Lee

I have noticed that all the discussion of engine improvement seems to deal with bolt-on or plug in changes. These work, but I haven't seen any discussion of "blueprinting, " head flow work or careful assembly matching.

Race engine builders (assuming the rules allow) focus on these, since the bolt-on allowances are the same for everyone. Depending on the engine, this can yield considerable performance improvement.

I'm wondering if anyone has in fact worked on this? ( I don't have any personal experience with Honda engines. I've built engines, but I paid experts for the high skill / expensive equipment operations.)

Start with basic "blueprinting" - making sure all tolerances are correct, balancing pistons, rods, crank, etc.
Manually locate crank TDC with a dial indicator to verify that cams are timed exactly. Use offset dowels etc. to correct. I suspect Honda is better than this, but I have had to adjust cams by several degrees, to get on spec and found timing marks on the engine off as much. On the S2000 engine, you would make sure the timing mark read by the ECU is exactly where is supposed to be.

Optimize flow through to whole system. Less resistance means more air/fuel charge gets in, and less energy is expended to get the exhaust out. Much of the flow resistance comes from surface drag. Improving flow requires polishing interior surfaces, but also taking great care that all interfaces match perfectly (manifold to head, head to exhaust, throttle body to intake manifold...) This includes the gaskets. Ideally the interface should disappear for air flow. If you fit a bigger header, but you have a big step where it bolts to the head, or even just a notch where the gasket isn't flush, you may just be worse off.

An engine builder will use a flow bench to monitor flow through the head as he carefully rounds off all sharp edges and bends inside the ports. "Porting" no longer means hogging out material. Engine builders say they get as much or more from careful detail work to eliminate points of turbulance and maintain a constant passage area. This could even include the ends of valve guides and injector openings

A race engine builder will also use a different valve grind, fit the pistons slightly looser and use different ring material. But these aren't durable for a street car.

Obviously this isn't cheap. Lots of expensive labor. But if I had an engine apart anyway, I'd think about it.

The other point of this rambling comment, if there is one at all, is that much of this also applies to the bolt-on mods. If you have either of the manifolds off, then by all means match the ports on head, manifold and gasket. Same for throttle body replacement, adding turbochargers, anything that touches engine flow. The brave will also smooth the square edges of the butterfly, while not reducing the diameter. Also smooth any butterfly fasteners that protrude from the throttle shaft or fill any holes in the shaft on the other side.

If you are going to spend the money for modifications, then spend a few extra hours on the installation to get the most from it.

Of course maybe everyone is doing this, and just doesn't write about it.

If you are competing the car, be sure the rules allow it.

Gregg

Road Rage

You make good points - I just wonder about the point of diminishing returns. As I recall, Honda does do some port matching. And in order to make an engine with a 9k redline, it had to do a lot of balancing and tight tolerance specification of the trueness of the bore, deck , pistons, crankshaft, etc. So perhaps there is not that much extra to be had, versus the cost of doing it. Racers do it because it could be the difference between winning or losing, measured in thousands of a second, over many laps.

Gregg Lee

I tend to agree, though it's unlikely they to individual engine port matching - just too much labor and time involved. Certainly I wouldn't expect the kind of results that Formula Ford engine builders get. They get over 115 hp from a Ford Cortina (and early) Pinto engine that was street rated at 75. A mere 50% increase. They do this with only a header, timing and all the detail work I mentioned. But this is an unsophisticated, pushrod, two valve per cylinder engine. Much rougher starting point.

On the other hand, when remove the hose from the throttle body, you can see a fat, round throttle shaft, and two non- countersunk butterfly attaching screws that stick all the way out the other side of the shaft. The inside surface of the intake runner is just as rough as the outside, with several mold marks. You can reach through the throttle to feel ridges at the bolted interface between the thottle body and intake runner. Is the head similar? I don't know. That's why I asked if anyone had played with it.

twohoos

Try a search for "Alaniz head".

PedalFaster

Agreed on both points.

Data point: Grassroots Motorsports built the engine in their '94 Celica to the limits of the SCCA Stock class autocross rules. To quote their article, "Our $3500 rebuild has netted us 4 horsepower" (although, to be fair, that's not as bad as it sounds -- it represents a 4% gain over their baseline of 91.3 hp, equivalent to 10 hp at the crank in an S2000). That cost-to-benefit tradeoff is a tough sell unless you have a lot of money burning a hole in your pocket and/or you're at the very top of a race series where that very small gain would make a difference.

Steve

Road Rage

[QUOTE]Originally posted by PedalFaster
Agreed on both points.

Data point: Grassroots Motorsports built the engine in their '94 Celica to the limits of the SCCA Stock class autocross rules.

VFROOOM

I think blueprinting is more of a pre-90's performance issue with American V-8's. Production cast iron blocks, w/pushrod valve trains and big swinging counterweight cranks varied in manufacturing tolerances so much that a increase in performance is found when these tolerances are optimized.

Thankfully, American manufacturers have had to build better engines to compete with the imports.

Gregg Lee

[QUOTE]Originally posted by PedalFaster
Agreed on both points.

Data point: Grassroots Motorsports built the engine in their '94 Celica to the limits of the SCCA Stock class autocross rules.

Hyper-X

Hey Gregg,

You bring up some really good points, and to a very competetive person or a person who values an incredible amount of attention to detail would persue blueprinting and balancing. I had this done back in 1992 on my Oettinger/Techtonics Rabbit GTI. While a lot of skilled hours were put into assembling the final product I still believe that an average person should not think about undertaking something like this until you've done everything else.

The cost factor and the resulting gain may not prove as effective (for example on an S2000) like installing an AEM CAI into an otherwise stock S2000. We dyno'd my GTI before and after and it didn't show any significant gains at all. While that's just one car, I wonder if it affects more along the lines of durability and reliability of the engine over the long term.

Unless you're planning on building car for a special purpose from the ground up, then I'd agree that since the motor would be all apart, it'd be a good time to bp and balance the internals... but otherwise, I feel that doing something like this should be the absolute last thing to do.

jimknapp

Hey, Gregg,

Always good to read your posts. No flames, just thoughtful responses.

While I've never blueprinted an S2000 (I know, that was your original question) I can tell you that it can benefit more than one might imagine. I did a small block Chevy here a couple years back and assembled the crank along with all eight pistons and rods (no rings, cam or timing chain) to check for final stroker crank to block clearance, and by sticking one finger into the 3.5" diameter flywheel flange I could spin the motor over. With ONE finger! To this day that motor still runs like a dream.

Also as a rough rule of thumb I believe you should be able to put 55 to 60 hp through each square inch of intake tract/throttle body. Most hot rodding folks tend to over carburate their motors seeking more hp. My belief is that the stock S2000 throttle body will pretty easily support 280-290 hp, rough walled or not. And as long as the individual port runners are about 1.25 sq. in. I think they can easily support the stock air flow.

But as we all know EVERY little bit helps.

Ciao,

Jim