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Discussion Starter #1
First off let me preface by saying this is not a street driven car, It’s a race car used exclusively for SCCA RallyCross, essentially an AutoCross on dirt where every run counts for cumulative time. We (myself and co-driver) run in the Modified 2wd class where almost anything goes for drivetrain. The car is fast, National Champion last year and second this year so it’s no slouch in current form but it needs more oomph, we are one of the lightest cars but also one of the lowest HP. We just don’t have the pull out of slow corners others such as Sentra SE-R’s have.

Current setup: D15B2 bottom end, rebuilt but essentially stock with a D16Y8 top end complete with intake, head milled .040”. According to the Zeal calculator it’s around 11.8:1 but understanding it’s off some because of the altered head volume. AEM cam gear to account for the deck height change, DC header, AEM dryflow intake. Running on S300 P28 and 101 octane race gas. Made 107 hp at the wheels at 6300 rpm and 94 ft lbs at 5500 rpm with a fairly flat torque curve with 80 ft lbs from 2300 rpm. Definitely a very modest budget build.

Goal is to get approximately 160 hp and around 140-150 ft lbs of torque as low as possible. Much more than that we probably couldn’t put down in the dirt and may make it harder to drive smoothly. We could certainly hit the HP goals with a further built NA motor but I don’t think we could see similar torque gains. After further researching options such as 90civichillclimber’s build it looks like a high compression, small turbo setup is the way to go. Looks like we could put together a setup that spools super quick and essentially drives like a NA car with power building fairly linearly. Of course we’re trying to keep things reasonable cost and can’t go too crazy. Reliability is also a huge priority since runs are cumulative. Car has only had one mechanical DNF in 7 years and it was broke axles.

Is the torque and low end goal realistic? Would a turbo motor fall on it's face at higher RPM's? I don't mind a plateau, just not a cliff.

So far I’m thinking stick with the Y8 head, intake mani and cam, should be fine for the goals. DSM 450 injectors. Generic charge piping should work, small is good. Maybe step up a bit from eBay for the intercooler.

So, since I’ve never built a turbo setup, my questions are:

Stick with the current long block and maybe a thicker headgasket and ARP head studs as theoretically the stock rods might be ok for the HP goal? Second option but more $$ is to find a D16Z6/Y8/Y7 builder. Buy new high compression pistons and H-beam rods, might make me feel a little better for reliability but is it really needed for the stated HP goals?

Cast Manifold for faster spool, is the Go-Autoworks mani really worth double a eBay manifold? I like the central wastegate port, with a small turbo I’d like to keep it as close to the block as possible to retain a full size rad. There’s also a Greddy mani on CL nearby.

Big item is what turbo to use, I keep coming back to a small Tubonetics T3 with ball bearings for faster spool but it’s pricy, for the modest power goals would any number of the various DSM, EVO, or other OEM turbos serve us as well and save bucks for another area? I’ve only seen a few non-T3 manifolds and I think they were T-25 what the best option for a non-standard flange turbo?

Is there significant benefits between name brand BOV’s and Wastegates over the cheaper no-names? Are you just paying for bling factor on the name brands?

Meth/water injection have any benefits at these power levels? It would be really easy to recharge a small reservoir after each run. For that matter why not run water/air intercooling vs. air to air?

Thanks in advance, I haven’t found a build with goals like this yet and maybe for good reason. I’m most concerned if the torque goal is attainable. If there is a better alternative I'm all ears.
 

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Gt1752
DSM T25

Your going to bend those factory d15 rods doing what you do

Your N/A build should already be making more hp/tq than 107/94 and if your head is milled to .040 you should be closer to 13/13.5 : 1 compression. A beast7 makes more power than that
 

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95 del sol turbo
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I wouldnt bother with the water meth unless you are having some cooling issues. It may help keep temps down. If its a short 5 minute run I wouldnt worry though. A little 16g turbo would be fine. I attached a dyno of mine with a gt2854r turbo and have great tq and good power. I would go with an internally gated system since your not going for big numbers. Also a cast manifold should be fine.

The d15's have alittle weaker rods then the d16's but under 200 whp should be fine. As long as the block is in good condition I dont see any problems with it. I wouldnt trust a cheap bov or wastegate. If anything breaks on them y risk having those broken parts go into the block or turbo. Get something proven for 100 dollars more. You can get the conversion kits to make a manifold adapt to any turbo.



Ive ran the season in autox with no issues(knock on wood).
 

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Two men shy of a group
99 civic sedan ex
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no need to build your block, i have a stock block d16y5 making 166/149. it might just be me but i wouldnt trust my motor to a cheap knock off bov or wastegate, seeing as a busted wastegate can cause you to overboost and blow the motor and a bov that doesnt function right will lower the life of your turbo. the only turbo i can suggest that i know will spool quick is an sr20det nissan t25 or dsm t25
 

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Discussion Starter #5
To be honest I was a little disappointed in the current tuning and think there are certainly some gains to be made with more dyno time and some tweaks but I think long term we want more than what we can get out of the D15 N/A. It was tuned at 6000ft but I'm fairly certain those are corrected numbers.

I'll take a good look at T25's and GT1752's. The more I think about it I'm leaning towards picking up another builder motor to shorten any down time. Internally wastegated would mean maybe i should take a look at the Greddy manifold on CL locally for $90.

What exactly is a Beast7? I've been trolling this board for a while and have yet to see that.

Thanks for the advice so far.
 

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a d15 beast 7 is a d15b7 with
-an a6 cam that is indexed correctly,
88 a6 cams use stock cam gear 89-91 are off half a tooth so you need to use a y7 or y8 cam gear to index it properly. a adjustable cam gear is best to index it perfectly if you are getting it dynotuned.
- a d16z6 intake manifold or d16y8 intake manifold, it works best if you can port the head out so it is roughly .5mm biger than the intake manifold at all points.

if you are going with a smaller turbo at smaller boost pressure wastegate flow will be important to keep the exhaust from robbing to much power up top, i would suggest a external wastegate, they can also be more accurate and will flow better than a internal, (for the most part)
 

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The Wife and the Car
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Best setup for D15.
D15 Crank
137mm Rods
27.25mm CR Pistons

Bump up your CR. 13.5:1 is the limit for pump gas.
I would start with something lower say 13:1
Get a good stage 1 or stage 2 D16y8 cam. This should get you to 145-165 BHP mark.

Cant advise you on the turbo. For that we would need to know your track. How tight is it. How many straight ways. What RPM do you spend most of your time in etc.
 

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a d15beast7 is

d15b7 block and head
d16a6 cam with y7/8 camgear(prefurably adjustable at 2* ret)
z6/y8 intake manifold
z6/y8 transmission
intake, headers, exhaust
some mild tuning would be best but not nessesary

i'd run a beast7 with a gt17...oh yeah i did :D ...90hillclimber bought my old gt17 setup to use and he can confirm the fact it insta spools, its like a supercharger, it was awsome ran it for a couple years...15psi out of that little bugger will give you more than you could want...my setup was also good for mid 13's in the quartermile so it had some umph to it
 

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MuthaFuckaUppa
2009 Civic Si Sedan
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571 Posts
WRX TD04L 13b is a pretty nice turbo.



My z6 @ about 18 psi with vitaras, stock length rods, head milled .024" stock valve train, ported head, ported skunk2, stock throttle body, custom top mount, 2.5" full exhaust, no cat, big back door intercooler from go-autoworks. I believe these were 3rd gear pulls.

If you stuck with higher compression the turbo will spool faster.
 

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()*#$(*$
93 Legend L Coupe.
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If those are your power goals, I will still recommend a stock D16 block, your Y8 head and a GT17 or T25 with a cheap HF manifold and adapter plate that you can make yourself, a 3" downpipe, and a good tune at wastegate pressure. You will never have to worry about power in turns again, especially with a good transmission.
 

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AUSDM EG8 Sedan
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107hp is a nice number from that setup - congrats
you would most likely get more torque with a D15b7/a6 setup though
if you are looking at turbo than i think a fresh start with a Z6 or JDM D15b VTEC would be the best option

this is my result from D15b7 with D16a6 cam and adjustable cam gear, D16z6 intake manifold, intake/headers/exhaust, chipped ECU, 98unleaded and crap ignition timing (ignition/dizzy were out but not too bad) (i still dont know what the spike is in the middle lol)

since getting the boost bug i have swapped out to a JDM D15b VTEC and get more outright hp (i think it was like 120ish last time i checked) but the torque has dropped off alot compared to the D15b7/a6



 
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