B18c4 down on power?


mjbjck

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Aug 16, 2018
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EK9, 2x EP3, A45 AMG
Hi Guys

I’m looking for a bit of advise or any ideas as i have come to an issue i cannot figure out.

Story behind it, i will be brief lol.

B16a2 engine bottom end went on the dyno As i was remapping due to install few extra bits which include.

Stage 2 skunk 2 street cams
skunk 2 pro series intake
skunk 2 springs and retainers

power was well down before the bottom end went, which i put down to bad compression.

Then i purchase a b18c4, stripped the engine down, Renewed rings, mains and big ends etc. fully honed. put the b16a2 head on the b18c4 block as i had all the work done previously. Ran engine in and done a fully compression test before take back to the Dyno.

I ran the car in with the same tune as the b16 which seemed fine on the AFR (I have a gauge in the car). Which is a bit odd as i thought i should of run a bit lean.

Any back on the Dyno my figures were ****, 140bhp was not running lean at all through the rev range. The vtec was engaging but seem to not gain any power. Im thinking the cams aren’t right for the piston compression, maybe completely wrong here, what do you guys think? (Pistons are stock)
 
Do you use adjustable cam gears? Are these properly dialed in? My experience of the accuracy of markings on cam gears is shocking - so you can't just set them to zero and expect that to be the same as stock - plus aftermarket cams should be dialed in.

You'll also have lost compression by fitting that head - no quench pads. Ideally you'd use PR3, P30 or P73 pistons. Lumpy cams do NEED compression.

I'm surprised its not lean - that affects the power if its excessively rich.
 
I haven’t got adjustable cam gears. I just set the clearance to the spec skunk 2 provided. There wasn’t anything mentioned about needing them.
The skunk 2 pro cams are more aggressive so I bought the street ones.

doesn’t seem to be running rich looking at the AFR when it was on the dyno. Also I thought you would smell the Unburnt fuel, esp in a garage when running.

Really stumped me this has
 
Running at idle its closed loop so it won't run rich then.

You'd always get the best from cams by dialling them in. You get a lift at a certain degree position. You then use a piston stop to find TDC PROPERLY and then a DTI to set. - In any case this makes a few hp difference max, and if you have stock cam gears you'll be close to something near anyway.

I wonder if its just the low compression. The B18C4 isn't high compression anyway and you'll have reduced it by 0.2. Stage 2 is quite wild and the main difference IIRC between street and pro is the non-vtec cam. Do you not have some stock cams to try?

I assume youve set the ignition timing with a light?

John
 
Yeah I have stock cams, that was my next thing to try. Timing is spot on, we tried yesterday and synced with s300.

mid I remember right stock b18c4 is around 160bhp. Losing 20 seems a lot plus with the up grades. Forgot to mention I also have 68mm skunk 2 throttle body.
 
I think 170 is stock but its rare for a b series to make stock power. Sign of a fanciful dyno usually!!
 
With an a2 head its now lower compression than with the c4, with the c4 being low compression to stsrt with this is a no no imo.

I think its probably the fact the tuner2 cams haven't got the compression to make any use of, that and the fact no adjustable cam gears. Stick a c4 head back on and some itr cams
 
Indeed - high power is from an effect created by the "valve overlap" on wilder cams which requires high compression to work. The rapidly outgoing exhaust gas kinda sucks in 'more' inlet air while both valves are simultaneously open for a brief time.

Its one of the odder elements of combustion engines.
 
Whilst the cams aren't a good choice for your current engine setup I think there is something else a miss here. Check cam timing.
 
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