Well not too long ago I swapped the p28 pistons for the JDM pm7 ones in my z6 for a 12:1 comp ratio. I waited the 500 miles to change the oil and the 500 after so i could step on it. When I did, it picked up quick and then it struggled like there was no gas and finally it went back to normal. It seems like if I step gradually it's fine but the second I step on it good it looses power.

Has anyone had this happen to them before? I thought about it and I think its my exhaust system. DC sports 4-2-1 header that's 2' into stock cat into 2.25 piping back. I think it might be too restrictive and could be the reason why.

Does anyone know what diameter exhaust I should have? Is it bigger for high comp?

Here's my setup:
90 STD hatch
95 d16z6
JDM pm7 pistons
DC sports 4-2-1 header
J's racing Intake with K&N filter
9mm Iridium spark plug WIRES, yes wires
NGK V power plugs
91 Si cable tranny ( OEM clutch with 3k )
Everything is obd1 so its ran by a stock p28 ECU

All HELP will be appreciated, thanx.
btw it does back fire...



Modified by z6_EF_obd1 at 8:25 PM 8/20/2006

 

You need to get your **** tuned man, you're running way too lean. Keep stepping on it or even driving like that and you will blow out your ring lands, your **** is detonating like crazy I bet. Get tuned, you won't believe how much fuel it's gonna need, mine was pinging in the high 12's AF on pump gas.

If you want a taste of how good it's going to be, go drop 60 bucks on a tank of 105+ octane, it will motivate you!

 

So just higher octane will do the trick, for now? I should still x the cat and go straight 2.25 piping though, right? And what tunning do you recommend?

 

yea man you definately need a tune. are you running the stock cam still? throwing those pistons in there isnt gonna help anything. you need a cam that closes your intake valve later so you wont have such a high effective compression ratio. invest in some tuning equipment. wideband o2, maybe uberdata, and that should be good. putting those pistons in probably just cost you at least 500 dollars, and it will blow up your engine if you dont do anything.

clif notes: its probably not your exhaust

edit: it backfires? something is wrong. what else did you change who did the work? cam timing is ok? any codes? how does it run part throttle?

what if its running really lean and the valves are getting burnt and leaking? anyone care to comment?

 

You will be fine on the stock cam but you need a tune. Before you drive around, read up on pgmfi.org or d-series.org. Most people on HT here aren't running stuff like this, the average Honda guy wants to drop in a (worthless) B16 and be done with it. Get your **** tuned, make that engine healthy, and you will be all set. There is a great thread about building a NA SOHC VTEC in the engine building forum on d-series.org. If you're still running ok, your motor is probably fine, but damn dude go easy on it!

 

well I did the work my self so i only spent money on the pistons, rings, head gasket, oil pump amd timing belt. But I just bought a 97 coupe with a 2000 front end and bad engine. Part of my cash went there an the rest was for the engine in it. For now what should I do? It'll take about 3 weeks before i can afford anything.
Use higher octane gas only?

 

The only thing you really can do is get tuned. If you can even get 100+ octane where you are, you will spend more money on it than you would tuning after a couple of weeks, that **** is expensive. Run 93 and drive like a grandma is all I can tell you, or don't drive it if you can help it. Get an LC-1, datalogging cable, a chip kit, and a BURN1 from moates.net, and start reading on PGMFI.org...

 

Thanx for the info downest and I only stepped on it a couple of times, It souds beautifull, not ricey loud, just deep and strong. As far as b16's go, the a6/y8 or my z6/zc combinations produce more power and torque for less cash, imo a better, wiser choice!

 

I only run 93!!! never less for my comp. but it still did that. Have you seen the people on ebay that will tune your ecu to your specs? and would you trust them? or do you know anyone that is good at it?

 

yeah its definately running lean and not tuned for that high CR
i'd suggest dropping an aggressive cam in there too to take advantage of that higher comp. BEFORE you tune it

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by z6_EF_obd1 &raquo;</TD></TR><TR><TD CLASS="quote">I only run 93!!! never less for my comp. but it still did that. Have you seen the people on ebay that will tune your ecu to your specs? and would you trust them? or do you know anyone that is good at it?</TD></TR></TABLE>

I have a friend up here who does mine... don't know anyone in TX. I don't know how someone on ebay would be able to do it for you.

 

Well he says he will tune it to your given specs and even use the CEL to work as a shift light and put a USB port or whatever you call that thing on it. You give him a list of the parts you have like header, intake, internals, comp, tranny and he'll tune and send it, if you want to you can send your core after and he will send you some money back, or so he says.

 

i dont see how he'd be able to PROPERLY tune your car without the vehicle being present.
ecu chipping is NOT "tuning" your car

i mean he's probably using a program like CHROME or something like that but every vehicle is different

 

Yeah, I suppose you could do that...


but don't.

 

all the parts from moates.net come out to around $335. Wouldn't it be better to use a Hondata s100?

 

You'll still need the LC-1, which is a majority of that cost. Get what you like, but you just need to be aware that having a high-compression SOHC isn't a drop in and go affair like a B.