D16Z6 SCCA Roadracing engine build question

[Xian]

Hi all,

I know this forum isn't directed specifically toward roadracing and is more tailored for drag but I know that you guys know your stuff when it comes to engine builds.

SCCA is in the process of working out the minimum weights for some of the Honda vehicles for IT (improved touring) roadracing and there has become some question/concern over roughly how much the 92-95 Civic EX/Si is going to be able to make in legal IT trim. The D16A6 from the 4th gen cars is already sorted and proven and the car has ben weighted accordingly but some are saying that the Z6 engine can't even make as much power as the A6...

Here are the rules for the build:
Intake, header, and exhaust are essentially open (no cold air intakes though)
ECU is open as long as it fits in the stock ECU casing
Stock cams, valves, crank, rods, pistons, etc... (anything not addressed here must remain stock)
Engine can be bored .40 over
Head can be decked resulting in no more than .5 increase in compression
Engine pulleys may be replaced with smaller/lighter pieces
Power Steering must remain attached
AC may be removed
NO cam gears

I apreciate any input from personal experience or even conjecture based on previous experience.

Thanks!

Christian

[Dyno Dave]

Hi all,

I know this forum isn't directed specifically toward roadracing and is more tailored for drag but I know that you guys know your stuff when it comes to engine builds.

SCCA is in the process of working out the minimum weights for some of the Honda vehicles for IT (improved touring) roadracing and there has become some question/concern over roughly how much the 92-95 Civic EX/Si is going to be able to make in legal IT trim. The D16A6 from the 4th gen cars is already sorted and proven and the car has ben weighted accordingly but some are saying that the Z6 engine can't even make as much power as the A6...

Here are the rules for the build:
Intake, header, and exhaust are essentially open (no cold air intakes though)
ECU is open as long as it fits in the stock ECU casing
Stock cams, valves, crank, rods, pistons, etc... (anything not addressed here must remain stock)
Engine can be bored .40 over
Head can be decked resulting in no more than .5 increase in compression
Engine pulleys may be replaced with smaller/lighter pieces
Power Steering must remain attached
AC may be removed
NO cam gears

I apreciate any input from personal experience or even conjecture based on previous experience.

Thanks!

Christian
I remember reading somewhere that Dave from SMSP runs a car in that series send him a PM or e-mail.
Regards Dyno Dave

[Xian]

I'll see if I can get in touch with Dave.

Thanks!
Christian

[kyle h.]

Are you allowed to use ARP hardware? If so, I'd suggest using at least the rod bolts.

wonder why you need to keep power steering?

[Levi]

I wonder why as well about the keeping of power steering. strange. i agree with kyle about the arp hardware, if the rules allow that, definately step up and use it where you can. sounds like the rules are pretty straight forward about all of this and I think it is totally possible to build a very competitive car with a z6 using those rules.

[jsi]

Christian (welcome, btw), I'd be surprised if there have been any "serious" IT-spec builds done on-here, or elsewhere for that matter. Maybe someone from HC did a build? I mean usually if someone sinks a few grand into a rebuild, it would make sense to build-up the head and throw some cams and compression in there. Until some SCCA-serious shops start building these engines to the limit of the rules, we can only guess the true power potential of such a build. But I'd be really surprised if an IT-spec Z6 would not match an similar-level built A6, which is typically around 125whp (dynojet) afaik...

[Xian]

Are you allowed to use ARP hardware? If so, I'd suggest using at least the rod bolts.

wonder why you need to keep power steering?

Nuts and Bolts are free, so yes, ARP rod bolts and studs where ever applicable :-) Most people seem to be running 4.9 FD and spinning the hell out of the engines so keeping them together may be a bit difficult long term.

PS is required to remain per the rules structure... I know it seems a little bit odd but that's just the way it is. The ruleset is very specific about what can be done... if it isn't "allowed" then it is, by default, "disallowed". The good thing is that you can underdrive the PS pump via a pulley change.

[Xian]

I wonder why as well about the keeping of power steering. strange. i agree with kyle about the arp hardware, if the rules allow that, definately step up and use it where you can. sounds like the rules are pretty straight forward about all of this and I think it is totally possible to build a very competitive car with a z6 using those rules.

Competitive is all going to be realtive depending on the vehicle weight. ;-)

Any input on whether or not 135whp sounds attainable?

[Xian]

Christian (welcome, btw), I'd be surprised if there have been any "serious" IT-spec builds done on-here, or elsewhere for that matter. Maybe someone from HC did a build? I mean usually if someone sinks a few grand into a rebuild, it would make sense to build-up the head and throw some cams and compression in there. Until some SCCA-serious shops start building these engines to the limit of the rules, we can only guess the true power potential of such a build. But I'd be really surprised if an IT-spec Z6 would not match an similar-level built A6, which is typically around 125whp (dynojet) afaik...

Thanks, you're on the Sandbox too, right? :grin:

I didn't think that I'd run across anyone who'd done a full IT build, but thought that I'd get a little input from some of the more knowledgeable drag engine builders to see if their gut reaction is "Yes" or "No". I believe that the engine has good potential and just wanted some 3rd party input :-) If the Z6 can match a fully built A6 then we're at least in the right weight ball-park. my A6 managed right at 126whp on a Dyna-pack with a crap header and stock ECU. With a better header and ecu, I should be in the low 130's... right about where the Z6 should be too.

[goforbroke]

I think with a properly built Z6 you could make 130-135whp. Even with the rule book limitations, but you are going to have to dish out some money for a decent header, like SMSP which is roughly $500. A nice velocity stack setup with a good free flowing filter like apexi if compatible. You can have fun with the exhaust, but dave could possible give you some feed back on what works with custom, depending on length and etc...
Are you able to touch the intake manifold?
The resuring of the head will help with compression like you mentioned. Their are other pointers such as running losser tolerances on bearings to free up some power.
All these parts won't make any decent power if you don't have a good tuner, hondata or chrome pro will get the job done for you.
Your really going to have to spend some time on the dyno, but you already probably know about that because in your class of racing, people spend hours on the dynoing trying to squeeze out and extra 2whp.

[rushi]

Rules seem to allow .040 overbore for cylinders, those could help valve shrouding and improve the flow(and compression/displacement too) a bit. Using P29's is not allowed, right? Even them are OEM?
How about some camgear from different engine, like D15, Y7/8 or something if those will give you ~4deg cam retard? It would surely help top end power a lot from my experience (my D15 with A6 cam was ~4..5degr retarded and very decent power 4...8k comparer to zero).
Dunno if these are allowed or considered as cheating, being OEM parts but not for this particular engine.

[Xian]

Spending money on decent parts and tuning is, unfortunately, a big part of the build. ;-) $500 header, tight head, and loose bottome end is pretty standard for a full IT build.

All stock parts must be OE for that specific engine. Unfortunately no mix and match allowed :-(

I appreciate all the input so far... it sounds like 130-135whp is very attainable for a Z6 engine. It'll cost $$ and take time to get there but it's not impossible.

Thanks again!

Christian

[martyr1391]

Hi Xian, Thinking about building an EG as well?

[4drman420]

i shall aggre with the 135hp is very attainable, i think i should even be pusshing that or really close with the very little mods i have but yah that does cost money i know but you should be able to reach that just fine.