Got my Prelude dynoed on Tuesday at Slowmotion Motorsports in Sunbury Ohio. If you are looking for a good tuner, and Columbus Ohio would be a reasonable drive for you, I highly recomend Corey Parrish at Slowmotion. I found him to be a very knowledgeable, personable, and courteous man. He answered my questions, talked to me about the results, and helped me try to find the problem.

The dyno is a Dynapack 2000, the results were not what I was looking for. 220 hp and 217 tq is not good for my setup which is Hondata s300, JRSC, Motorvations jackshaft pulley. What we found was that max torque was achieved at only 4000 rpm, with 165 hp at that point. Max hp was at about 6300 rpm, where tq had fallen off to about 185 ftlb.
A look at manifold pressure at it was dropping, in almost a straight line from a max of 9.8 psi at 4000 rpm to a low of around 6.5 psi at 7500 rpm. Not good. Whatever the reason is for the psi to not be holding, we couldn't find it. I don't fault Corey for this, as we tightened the jackshaft pulley and the main drive belt pulley, which helped some, but not much.

I am looking for suggestions as to why the blower is not holding pressure. If you have run into this before, or have any ideas, I would be glad to hear them. We put on a new jackshaft pulley belt the day of the dyno test, along with the install of the Motorvations pulley. The main drive belt was at max adjustment, have a new one already bought. Going to check the pcv valve, egr valve, and are trying to figure out a way to block the bypass valve in the closed position to see if the bypass is leaking pressure somehow.

There should be another 30 hp or so, and maybe a little more torque in there that we are not making.

 

I know you said that your blower belt was tight,but every time I had a problem like that it was because of bad belt alignment, so it would slip. Make sure your alignment is PERFECT and tighten it up some more. try a different brand belt if that doesnt work. This problem is common, I always had to overtighten my belts

 

your tq seems very good. care to list the details of your setup? when does vtec engage and has any cam gear tuning been done? your definately choking up top.

 

bad bypass valve maybe?

 

Setup is cai, RC550 injectors, Walbro fuel pump, Motorvations jackshaft pulley which is supposed to raise boost to 9-10 psi, S300, stock header and 2 1/4 inch exhaust with a highflow cat. Vtec is at 3200 rpm. Tuner believes the header and exhaust are holding me back, and I would agree. But, it would seem to me that if the exhaust is restricted psi should be going up, not down.

Spoke to Keith at Moss Motors and he suggested wiring the bypass valve closed, remove and plug the vaccuum line to the bypass valve to test. He said it will run badly at idle, but would prove the idle valve good or bad at wot.

I have included the dyno sheet.

 

Yah ur defintely choking, and theres prob some belt slip coming into play as well, or a boost leak. try that bypass valve check u were told, and either get a real header with 2.5-3" collector and a FULL 3'' exhaust, including 3" cat, or run the stock pulley. Ud prob even make more power with it, going by all other jrsc dynos ive seen. other that that setup seems nice. enjoy that tq!

 

opening up the exhaust will actually make the boost drop slightly because of more flow, but yes still make you more power. Everytime I have boost max out at mid rpm range and then fall off is always a belt issue. In my case it's as easy as tightening it. I'm sure your belt is slipping one way or another

 

I have been looking for a reasonably priced ($300-$400) header and there doesn't seem to be much out there. Has anyone tried the Subliminal/Kiddracing header for the Prelude? I am also not sure if I am better to get a 4-2-1, or 4-1. Definitely want at least 2.5 inch. Car is slammed, not much room under there.

Any ideas, new used?

 

I got a Kamikaze 4 - 1 header with a 2.5" collector. Works nice. Just be sure to not use the bolts they supply or else they will come lose and fall out.

 

Just have CP at Slomo make you one or let them get you one. They did a custom 3" exhaust on my hatch and I am running a 4-1 header. Also, I am running a JRSC on my B18C, exhaust made a huge difference. Good luck!

 

I know RMcdaniels's m90 setup tossed the belt after a lap due to stretching, despite the belt starting as tight as possible, and pre-stretched. He then used a Ford Lightning auto-tensioner setup. For your belt situation, I can suggest a two things. Make a riser plate for between the SC and manifold, sort of like a VQ35 plenum plate. That would raise the SC, allowing you to get the belt tighter. May even help power, depending on it's thickness. For the main belt, you could add a B/D-series t-belt tensioner to help take up slack, also tightening it. Of course smaller belts would work too, this is just if you can't aquire them, or they won't fit w/o being stretched first.

My other guess is that you got a used JRSC that has too much clearance inside. Sometimes the coating comes off and/or the rotors/housing just get scratched up too much. Since it's a possitive displacement pump, any extra clearances inside will lead to reduced flow & pressure.

One uncommon issue is sometimes your bypass valve doesn't seal completely. Boost will leak out of it, although more at lower RPM's than higher RPM's.

 

if the bypass valve diaphragm goes bad it will stay shut not open. so unless there is an obstruction keeping it open it should not be a bypass valve problem

 

your problem is the belts are still slipping. I just installed my jrsc and had it tuned. After I got on the dyno we did some pulls and boost would stay around 9psi until about 6k rpm and then it drop off gradually till 7krpm I was barely boosting 5psi. tightening belts didn't help either. we also couldn't hear them slipping so we didnt think they were. So when I got home I tried everything imagineable to get them to stop slipping and still no luck. after exhausting all options that supposedly remedied this problem, what i eventually ended up doing was adding another pulley. I'm at work so I can't get on photobucket but if you look on preludepower.com or preludeonline you'll be able to see the pics. It's right after the jackshaft pulley which gives the belt more wrap on the pulley. After I added the pulley I can hold 9psi of boost all the way to 7.5k rpm. Also what I did was (probably get flamed for it) but I took a pair of vicegrips and systematically clamped them onto the actual pulley itself, putting little teeth marks on the actual ribs of the pully. I don't know if it's soley the added pulley or a combination of both, but i have 0 belt slip now. I also run a bit of belt dressing. maybe it was a combination of all three, i don't know. I also did the vice grip trick to the passenger side jackshaft pulley. either way my belts don't slip any more and it makes me happy

 

think about it you are forcing the car to breathe in but not letting it breathe out. and dont be cheap on the header! you got alot of good parts you will probably see 25+ whp just by letting the car exhale and retunning it. dont listen to me i pay someone to tune my car because i get along with electronics as well as water does, listen to YOUR tuner there is a reason you pay him(he does it every day)! Or leave like it is its not my car my B18 put down 378 WHP

 

agreed. go with a 3" exhaust and you'll see a lot more gains. just be happy with your numbers...way better than mine. I only made 189 torque and 214whp...and that was on this setup

9psi accord crank pulley
525cc precision injectors
walbro 255 fuel pump
kamikaze header
3" header back exhaust w/mandrel bends