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Discussion Starter #1
Z6, vitara 75.5/fjt rods. I did a compression test before I swapped the stock cam for a delta 272-2.

Stock cam, all around 150psi. I'm also at 6000'.

I threw a delta 272-2, and oem head gasket in(old, cheap fjt rebuild kit one was pushing water), when I put the turbo on, a few months ago.

I decided to see what the new cam would give for compression numbers. Today I got 130,100,115,112. Warm engine, throttle WFO, cranked it about 10 revolutions. Did it a few times. (been using torco 5-30 synth)

I actually did it last week too, but didn't write down the numbers, basically the same spread, just all were about 10 lower. I adjusted the valves. .006/.008, on overnight cold engine. same results, adding cap full of oil to cylinder didn't improve the 90 number, last week. I double checked the valve lash, the engine wasn't overnight cold, but had sat for a few hours. same results.

So, fearing the worst, I do a leak down test. again, warm engine.(100 psi)
7%, 7%, 7%, 5% pulling the dipstick out is where I hear the most noise.

Any ideas as to why I'd have the big spread on the compression test, but good leak down #'s? (the cam is advanced 2deg on the adjustable gear, but i haven't degree'd it, so who knows where it really is)
 

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You really don't know much about how cams work, do you? (I don't mean that as an insult or being condescending, just asking.)

A "performance" cam will lower the dynamic compression at lower RPMs trading it off for higher dynamic compression at higher RPMs. (Normally.)

Does the car run fine?
 

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Discussion Starter #3
Yeah, I understand the lower/higher dynamic compression. What I wasn't expecting was one cylinder reading 130 while the next was 100. I figured there should be less of a spread.

The engine does run fine.

I checked the compression because I was curious how low it was going to be with the 272 in there.
 

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Discussion Starter #5
Sooo....

Seeing as I have the day off, and I was up early, I decided I'd swap my stock z6 cam in, and see what my compression was.

I took the car around the block, warming it up, then did another compression test with the delta 272.

#4 still 130, #3 still 100.

I start into pulling the cam. standing there with the valve cover off, I decide to check the valve lash, one last time. (Previously I'd checked it a few times total, and was pretty sure they were good.)(.006 intake, .008 exhaust)

#3(the low cylinder) seem fine.

spin the crank to check #4(the 130 one) One of the intake valves feels a little loose with the .006, try the .007, it fits, try the .008-if I force it it will go. try the .008 again-this time it fits-WTH? try the .009-its tight, but it also fits.

Stand there for a minute looking at the engine, trying to figure this one out.

Try the .008, this time it won't go?

Then I realize i had gone at the valve from different angles with the feeler gauge.

try again-the .009 goes.

the Vtec solenoid, along with a few other things, kind of crowds the intake side #4 cylinder. I was angling the feeler gauge into the valve, if I flattened the feeler gauge, the tight ones slid right in.

I think the combination of my valve adjusters being more angled, 'cause of the smaller re-grind, plus my angled approach on #4 intake, was messing up the "drag" of the feeler gauge.

I re-adjusted the lash, ran a quick compression on #4- 110... (SOB...lesson learned...)
 

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Discussion Starter #7 (Edited)
Update.

so my last post It seemed I had fixed the problem.

since then, I still get 130, 100, 115, 115. I've adjusted the valves a few times and its always the same spread.

I blew the head gasket two weeks ago, #4 blown, #3 was fine.

New head gasket, same compression numbers.

Also, my leak down numbers were all about 6-9. BUT for the #4 I usually had to stop just before tdc, hold the crank, put a little air in the cylinder-then move the crank a bit more. it would leak a bunch till I moved the crank a bit more. then it would seal up.(I do have my cam advanced 4-5deg) (One of the #4 exhaust valves leaks a little air, if I put a screwdriver on the top of the valve and wiggle it, it leaks more, doing the same to the valve next to it does nothing)

anyways, sent my other z6 cam in to DELTA and told them I thought something funny was going on with my first cam. had them grind another 272-2. (they said call/sent them the cam back if my compression #'s were back to normal with the new cam)

Got it back this afternoon.

Put new cam in, fast idled it for 20mins. let engine cool for about 15mins, then ran a compression test.

120, 120, 117, 120

Going to re-adjust the valves in the morning with a cold engine.
 

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Discussion Starter #9
So I adjusted the valves this morning on the cold engine.

Took it out for a quick test drive/warmup.

I'll fast forward to the compression #'s on a warm engine.

122, 120, 113, 120

Did a leakdown too

6, 6, 6, 6,

and while I had the compressor fired up, a boost leak check. No leaks noted.

Quick testdrive impressions.

I have 2 widebands. a LC-1 running thru neptune, and a pillar mounted prosport uem.

Before, my prosport usually read about .5 richer than what the dyno and my lc-1 said. It would kind of jump around a bit to(.5), like the stepper motor in the mechanical gauge was messed up. (I actually sent it in to get tested when I first hooked it up because of this.)

Now its much smoother, and reads about .2 richer than my lc-1 now. also my afr's are more steady on the lc-1.

I went to the dyno a few weeks ago. When I drove it the next day, my idle afr's were quite rich, so I leaned out a few columns.( the tuner guy didn't zero out my iat tables, and I believe these were messing with my tune(specially when I was spraying meth and nitrous and my iat's would drop way down, so I zeroed them out, and adjusted some) Today, my idle afr's were lean, and when I adjusted them back to 14.7ish, I was back to exactly the same numbers as the original dyno.

I had also done a bit of tweaking through the map, from the dyno's results. I didn't data log earlier, but was watching the afr's. I had them pretty smooth, but now they look a little messed up-right in the areas I adjusted.

Going to load back the dyno tune and do some data logging.

I'm thinking that my previous, messed up cam, was screwing with my afr's and the dyno's sniffer wasn't as thrown off as my lc-1 was 'cause of it.
 

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I wonder what my compression ratio would be. I have the same cam. I haven't even done an initial compression test. It still runs fine after 2000+ miles.

Side question, when you adjust the fuel maps after being dyno tuned, is it necessary to change the ignition maps a bit? I.e. going from 10.7 afr WOT to 11.5 afr.
 

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Discussion Starter #11 (Edited)
I'm still very new to tuning, so take that into consideration.

I don't mess with my ignition tables at all. Sitting next to the tuner on the dyno, he was explaining all the stuff he was doing, both the how & why.

With the timing-the dyno had some number that basically represented torque. he would play with the timing, say like in the cruise areas, and you could see the "torque" number go up and down(real time) thats how he adjusted the timing, part throttle.

Full throttle timing-he would do a pull, adjust the timing, then do another pull. then he would transpose the two pulls on top of each other and see how the torque/hp curves looked.

after he got it where he liked it, we put fresh plugs in, did a pull & shut down. He would study all the plugs with a magnifying eyepiece for a bit, to confirm the tune.

I wouldn't know what to do about timing without a dyno-I'd have to do a pull & shut down and look at the plugs. But I wouldn't really know where in the maps or how much to adjust the timing, I don't know enough yet.

I told him I didn't care about the numbers, wanted a conservative tune.

Hopefully my tune is conservative enough that I can adjust my afr's a bit and not have to worry about timing.(i don't think he ever left it at peak torque, he would find peak, then hit the keyboard a few times adjusting back.)

There is a fuel distributor right down the street that has Sunoco 260GT at the pump, 100 octane.(my nitrous supplier is right next door to ) :)

When I play with my afr's, I usually fill up with it-hopefully that gives me enough safety buffer so I can play around a bit.(I have meth/water injection too, so I have a pretty big buffer zone)
 

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Wow I just ordered my delta cam. I hope I dont run into the same problem.
On a side note. Repeated requests for a cam card drew a blank or no responce.

I did a search. And could not find a single article or post explaining how to setup the Delta 272-2. All I need is something as simple as a cam card or a Lift at TDC for the intake and exhaust.

If Ive missed this info in my repeated searches a link would be a big help.
Im suprised nobody has profiled this cam. I get about 200 PSI at 3000Ft. with the stock cam. Will post my delta numbers in a few days.
I dont know why but all the cams tested so far seem to want to be retarded to work. Straight up never seems to work. I wonder why.
 

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i have the same problem, delta 272, no matter what i do its running pig rich...

Ill try with compression test...
 

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wow what a threat for me. But the rocker arm ratios seem off.
As does the total lift off the cam.
Im going to see if I can generate a rough profile for my simulator with this data till I get my cam in hand.

Pig rich compared to what ? I dont understand ?
If your talking NA yes. It wont breathe as well as a stock cam. I had that problem when I installed my Bisi 2.4 the car ran like crap. But that was because I was in NA mode. And this profile has little or no over lap. It should work find with a Turbo.
What is going to be interesting will be comparing how installing the cam effects my fuel tables. It will clearly indicate where the engine is breathing better and where its worse.

Im up to 11.2 PSI on the stock map sensor. And my map is created for the stock cam.
 

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Discussion Starter #16 (Edited)
I just went out and did a some data logging. low, med, high cruise, and a few 3rd and 4th gear interstate pulls- from 9-18psi, with and without meth.


I loaded the original dyno tune in, zero'd out most of the iat's, zero'd out some of the tip-in(those were messing with me too)

afr's look pretty good-better than when I had messed with them, and over the entire map...

So the other cam seemed to be really messing with my wideband readings.

now to call Delta...
 

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Discussion Starter #17
Just got off the phone with Delta, they said send it back, they would try to regrind it, and give me my money back.
 

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Discussion Starter #19 (Edited)
I"m running ID1000's, on pump. I don't think some of the corrections in Neptune, like IAT's are automatically scaled correctly for the bigger injectors. so if the computer thinks it needs to add a correction factor of +10, +10 of 240cc is a lot different than +10 of 1000cc. I don't know if its true, but I'm suspecting so. (I'm suspecting the same with "altitude compensation" enabled-I go from 5000' to like 11000'. I have to add fuel, it goes leaner the higher I go up-it should go rich I'd think. I can't change the correction factor though, and I'm going to disable and see how it acts.) (I switch maps at like 9000', to one that I just kind of added fuel to, its not real precise)


when I spray meth my iat's would drop, and the "iat map"(VE Tables) would start adding fuel, the colder it got the more fuel it would add. when I'd spray the nitrous, my IAT's would go from like 104 to something like 50-by the end of the run-computer would add a bunch more fuel till the iat's came back up, and I'd go rich for a bit.

plus its cold out here in colorado. when I'm cruising, my iat's are like upper 90's, and sitting at a stop light they go way up, but when I mash the gas & get some air moving thru the system, my intercooler works very well and my iat's drop to like 80deg. computer was dumping to much fuel then too...

and the iat's move kind of slow so not that accurate over short term.

It was messing my afr's up because the temp changes weren't constant. you could see it in the data logs. Zero'd out has less effect. I'll slowly add it back in if I need it, to get more precise on the tune.

I left the low load iat's active, I actually had to add some fuel as the iat's increased. Med and high load I mostly zero'd out, except when it got down really cold I left some in there. I'll see what happens when it gets really cold out this winter.
 

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Discussion Starter #20 (Edited)
I dont know why but all the cams tested so far seem to want to be retarded to work
here is the difference going from +2, to +4 on the cam. (I didn't degree it, so who knows where it really is.)

I lost a bit top end, but it spooled better. I left it advanced, but I'm planning on moving it back a bit next time i'm on the rollers and see if the top keeps climbing. It doesn't look like much on the graph, but it made a big difference in how the car felt driving. (Spool isn't a concern any more since I installed nitrous...)

 
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