ok i just tuned my car recently on came across some nasty droping of the torque after peak VE @ 6050rpm. this graph is very similar to an older set-up (with less money invested) that made 213whp/185 ft/lbs @ 7psi (on an FMU with no timing retard). the only things left that had not been changed between the two were the skunk 2 IM and the 2" charge piping. after reading http://forums.evans-tuning.com/viewtopic.php?t=415 i think i may have nailed down the issue being the 2" charge piping.




to get notes about the tune, it was 17* timing @ peak VE going up to 19* at redline. target a/f was 11.7 and was within .1 across the board.




thats 242.2whp and 197 fl/lbs @ 11.5-12psi. also 219.5whp and 180.5 ft/lbs was the peak @ 10psi. also to note the temp as measured by the dyno was in the 93-95 degree range so it was hot in there.

Turbo set-up:
GT3076R w/ TO4S .70 a/r compressor housing and .82 a/r turbine housing
ATP oil inlet restrictor (.035") w/ 4 -an feed
ATP oil return flange and and 5 deg tilt return flange for the pan
Peakboost manifold (first made for a d-series )
Peakboost 3" DP (open) and WG dump
Tial 38mm WG
HKS BOV
JRC 8" FMIC
2" charge piping all the way around

Engine:
Stock head
Zex 59300 cam
Skunk 2 IM
B18 TB
Stock bottom end
Mr. Gasket crankcase evacuation system
Unorthodox ultra-r pulley
ARP head studs
Felpro HG
Ishihara-Johnson teflon crank scraper

Fuel management/Spark:
Hondata S300
RC 750cc's
PLX devices M500 wideband o2
Walbro 255 fuel pump
MSD 6a box
MSD plug wires
MSD blaster 2 coil
H22/H23 distributor cap
7-series NGK's
R1 grounding kit

Tranny:
Stock everything
CM stage 3 clutch
autozone axles

do you guys think my charge piping is the problem?

 

nobody has any insight?

 

Is it that your entire IC piping is 2" or just from turbo to intercooler. Anyway from reading your setup that diameter pipe sounds small. Sometimes when you have a problem,try the cheaper solution first. Your problem might be caused by something else but changing the pipe is easy so try that first. Try 2.5" from turbo to intercooler and 2.75" from intercooler to intake

 

yeah its 2" all the way around. i was thinking of starting with 2.5" all the way around being that the turbo outlet, intercooler inlet/outlet and TB are all 2.5".

 

Shouldnt the 2" charge pipes just give you really quick spool and not effect the horsepower that much?

 

well thats what one might think. did you read the jeff evans thread?

 

Thats you problem right there. The 2" Limits your top end, your engine is not breathing properly at higher RPMs

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by namm &raquo;</TD></TR><TR><TD CLASS="quote">Thats you problem right there. The 2" Limits your top end, your engine is not breathing properly at higher RPMs</TD></TR></TABLE>

yeah thats what im thinking. im wondering if anyone else has had this problem before, or has seen it.

 

A SOHC I built had a the same problem it had 2" piping too, I changed it to 2.5" all the way around and put on a bigger intercooler (original was way small) and it made a huge difference. when I told you 2.75" earlier is because I was thinking you had a B18 motor. Work with 2.5"

 

SOHC engines have poor ROD/STROKE ratios, so piston speed at higher RPM is very fast. THIS is why the engine makes great torque at lower RPMs and falls off sharply after. head porting would help with this problem too. You see as the pistom moves downward on the intake stroke the the heads ports is not allowing enough air to flow into the cylinder at the increasing piston speed. If you have access to B16A dyno sheet look at it and you will notice how flat the torque curve becomes at high RPMs like 9000. This is because these motors have good rod ratios 1.74, your motor is 1.52. The higher the ratio the beter the engine breathes at high RPM. By the way I see you are using a .82 ar exhuast housing. I think this is too big for your motor I would changed this to a .63 ar. This will move your graph to the left meaning you will be making more power earlier. Peak horsepower is not everything, your engine spends most of its time between 4000 to 7000 so if you make more power in this area it means faster times


Modified by namm at 7:18 AM 9/16/2006

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by namm &raquo;</TD></TR><TR><TD CLASS="quote">SOHC engines have poor ROD/STROKE ratios, so piston speed at higher RPM is very fast. THIS is why the engine makes great torque at lower RPMs and falls off sharply after. head porting would help with this problem too. You see as the pistom moves downward on the intake stroke the the heads ports is not allowing enough air to flow into the cylinder at the increasing piston speed. If you have access to B16A dyno sheet look at it and you will notice how flat the torque curve becomes at high RPMs like 9000. This is because these motors have good rod ratios 1.74, your motor is 1.52. The higher the ratio the beter the engine breathes at high RPM. By the way I see you are using a .82 ar exhuast housing. I think this is too big for your motor I would changed this to a .63 ar. This will move your graph to the left meaning you will be making more power earlier. Peak horsepower is not everything, your engine spends most of its time between 4000 to 7000 so if you make more power in this area it means faster times


Modified by namm at 7:18 AM 9/16/2006</TD></TR></TABLE>

yes i know all of that, i planned this set-up to do exactly whats its doing. trust me the powerband is fine now and will even better with an 8/8.5k redline. this project is the result of about 2 years of research i knew i was in for full boost at 5-5500, and that was the plan. i am not worried about power sub 5.5krpm only whats above.

i have looked at the piping issue before and not though much of it since im still below the "accpeted" .4 mach air speed. but with all factors being considered the charge piping is about the only thing that can explain a 25lbs drop in 1krpm. plenty of stock port/valved z6 have using a 59300 cam pull to 7.5krpm fine.

 

I see you have done your research, when you get it sorted out post it so I know. I love the interest in SOHC. Its like uncharted teretory. My car has a B18C motor but alot of my friends have SOHC and these little engines are like a secret weapon. they will kick my *** if I am not carefull . my best time was 11.8 on 12 psi and my friend ran 12.4 on 12psi with a SOHC, both cars are EK hatches

 

thank you namm for your input. does anyone else have an opinion?

 

anyone else want to throw in there 2 cents???

 

gt30r

 

do full 2.5 inch and you should be fine, i'm making 400whp with 2.5 in piping

 

thanks for your input. im thinking of getting a 68mm TB and running 2.5 turbo to IC and 2.75 IC to TB and just be done with it.

 

Sohc engine do not have poor rod strokes yours just makes poor power.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by MidShipCivic &raquo;</TD></TR><TR><TD CLASS="quote">Sohc engine do not have poor rod strokes yours just makes poor power.</TD></TR></TABLE>

ummm ok thats real intelligent. i now feel stupider for having read that post.

 

Fact/joke!

 

I wonder why honda did not put a 8200 rpm limit on it. A 16oocc SOHC motor has A crank throw of 90mm . A B18A LS motor 89mm BOth of them has rod lengths of 137mm. A LS motor is considered to have poor rod ratio in comparision to the B16A. This is why Both SOHC and LS motors come with mid 7000 RPM limits from factory and a B16A comes with 8200 LIMIT. I am not saying these engines cannot rev to 9000 RPM but they will be under more stress and therefore will not last as long under these conditions. I am just stating the facts. However we all push our motors beyond there limitations, rules were ment to be broken

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by namm &raquo;</TD></TR><TR><TD CLASS="quote">I wonder why honda did not put a 8200 rpm limit on it. A 16oocc SOHC motor has A crank throw of 90mm . A B18A LS motor 89mm BOth of them has rod lengths of 137mm. A LS motor is considered to have poor rod ratio in comparision to the B16A. This is why Both SOHC and LS motors come with mid 7000 RPM limits from factory and a B16A comes with 8200 LIMIT. I am not saying these engines cannot rev to 9000 RPM but they will be under more stress and therefore will not last as long under these conditions. I am just stating the facts. However we all push our motors beyond there limitations, rules were ment to be broken</TD></TR></TABLE>

true but looks at LS/VTEC's they rev to 8-9k all the time, given the supporting mods have been made.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by tannerLSt &raquo;</TD></TR><TR><TD CLASS="quote">do full 2.5 inch and you should be fine, i'm making 400whp with 2.5 in piping</TD></TR></TABLE>

how much psi??

 

you guys are looking at this in the wrong way, the piping size needs to be determined by air velocity through the piping. After a certain point ( .44 mach i think) you will have more backpressure inside the piping which of course is bad and the actual size is limiting the flow of air, I HIGHLY doubt you are having issues with your piping. I made upwards of 400whp on 2.25 inch piping, you need to calculate the air speed in your pipes there was an excel file somewhere that would do it for you but i cant find it search around. I dont think its the pipes probably something else...

 

https://honda-tech.com/zero...02591

Figure out your cfm and enjoy