285 Cam - Less Power Than Standard!

[dimmapalmer 0]

had my head port polished at shenpar and a 285* cam stuck in.

 

Before this my car had 133bhp at the crank.

 

just had it all set up again - and its got 100bhp at the wheels. and correct me if im wrong, thats about 115/120 at the crank? and the bloke who set it up knew how to do it properly, bigger jets etc etc. It went in with 88 at the wheels.

 

any ideas whats going wrong? just tried ringing shenpar but no answer...

 

cheers

[welshpug 1,627]

not enough compression for the cam, differences between Rolling roads.

 

what was the ATW figure when 133 bhp ATF was recorded?

 

Should have been far more than 133bhp with ITB's on a standard healthy engine.

Edited March 5, 2009 by welshpug

[Anthony 1,000]

Is the cam actually timed in properly with a vernier, and the ignition advance adjusted to suit?

[aCe 0]

Agree with Anthony, unless the venier is set up properly it will just sapping power! (presuming you have one of course, which i hope you do)

 

Who set it up for you, and how did they do?

[mattbenselin 0]

What's your compression ratio?

 

I know you ideally need more CR with a beefier cam.

This is not a hi-jack but I have yet to finish building my engine so have not ran it yet, I'm using a 285 cam with the CR about 10.2:1, is this enough?

[welshpug 1,627]

probably need closer to 11-1 to make the most of it IMO, easy to do on a 1.9, 1.6 pistons.

[mattbenselin 0]

When I took the head off my engine I found it to have dished pistons, the type found in the DKZ (Cat) model so to raise the compression I had it skimmed 1mm I think (I took the original depth of the chambers to be something like 7.5mm and skimmed 1mm off as if it were still that depth, follow?) How much more would I need to take off to get upto around CR 11.x? and could the head take it? How much of a difference would it make to go up another point (10.2-11)? And anything else to consider?

 

Thanks

[CaptainK 11]

Before this my car had 133bhp at the crank.

 

just had it all set up again - and its got 100bhp at the wheels. and correct me if im wrong, thats about 115/120 at the crank? and the bloke who set it up knew how to do it properly, bigger jets etc etc. It went in with 88 at the wheels.

ATF (crank) Rolling Road figures should be ignored as they are guessed / calculated based upon what is read at the wheels.

 

So based on your statement above, your car went in with 88bhp at the wheels and came out with 100 at the wheels? I'd say thats a big increase and should be happy with it !

 

I'd guess if it went in with 133bhp crank & 88 wheels previously that the previous Rolling Road session person was telling your porkies that your car was losing 45bhp (133-88) through the transmission. My original 1.9 GTi was 88 bhp at the wheels and that was "calculated" to be around 115bhp at the crank.

Edited March 6, 2009 by CaptainK

[Anthony 1,000]

I'd guess if it went in with 133bhp crank & 88 wheels previously that the previous Rolling Road session person was telling your porkies that your car was losing 45bhp (133-88) through the transmission. My original 1.9 GTi was 88 bhp at the wheels and that was "calculated" to be around 115bhp at the crank.

I took that to mean that prior to the headwork and cam, his car was RR'd at 133hp@fly. Since getting the headwork done and cam fitted, the car was initially 88hp@wheels when it went in to be setup on the rollers, and after setup, was 100hp@wheels.

 

Always difficult to be sure without knowing what other cars are getting on the same rollers, but no doubt 100hp@wheels does sound low for the spec - I'd expect a healthy standard 1.9 to be getting around 100hp@wheels. Obvious question is ignoring the figures for the moment, how does the car feel and perform on the road/track, as to me that's far more important than an arbatory figure?

[tom_m 0]

When I took the head off my engine I found it to have dished pistons, the type found in the DKZ (Cat) model so to raise the compression I had it skimmed 1mm I think (I took the original depth of the chambers to be something like 7.5mm and skimmed 1mm off as if it were still that depth, follow?) How much more would I need to take off to get upto around CR 11.x? and could the head take it? How much of a difference would it make to go up another point (10.2-11)? And anything else to consider?

 

Thanks

 

D6B pistons are dished too

[James_R 3]

so do 1.6 engine's aswell, seems only the BX GTi/405 SRi engine had flat top pistons in them.

[jimbean 0]

i have recently put together a 1.6 xu

 

i also used the piper 285 with a port and pollish/ crank knife edge/ total seal rings

 

on the cam info... note... should not be used with standard ecu/ only carbs/ throttle bodys

 

ours is on 45 and pulled 125 at wheels on rolling ooad

[James_R 3]

It can work on std injection, it's just not very good at idling and low end is adversely affected, but it does work. I'm in the process of making a 1.8 8v with a 280-285 deg cam on std injection, hoping for 135-140BHP.

 

Jim where did yours make peak power?

[C_W 3 1 Cars]

As already said surely if it "went in with 88@wheels" and now has 100@wheels is gained 12bhp at the wheels?

[BackStreetRacecars 3]

i have recently put together a 1.6 xu

 

i also used the piper 285 with a port and pollish/ crank knife edge/ total seal rings

 

on the cam info... note... should not be used with standard ecu/ only carbs/ throttle bodys

 

ours is on 45 and pulled 125 at wheels on rolling ooad

 

 

 

What was the head spec on this?! What size of jets and manifold make??

[SimonJ 2]

As already said surely if it "went in with 88@wheels" and now has 100@wheels is gained 12bhp at the wheels?

 

 

The gain from 88 to 100 seems to have been from the set-up session on the RR (after the initial power run when the work was done).

 

I'm keeping an eye on this thread as my car is away getting carbs/285 fitted. Of course I'll report when I get my results.

[jimbean 0]

It can work on std injection, it's just not very good at idling and low end is adversely affected, but it does work. I'm in the process of making a 1.8 8v with a 280-285 deg cam on std injection, hoping for 135-140BHP.

 

Jim where did yours make peak power?

 

 

our engine power band is fro 3500 good power is at 5 ish at limit is set at 7

 

we rolling roaded at boggys so no didgy print out

 

head is my flow spec with standard size 3 angle valve

 

total seal rings and lightend bottom end

 

our run in session did not go quite to plan as the tuner set the timing not to tdc through the lightend flywheel removed tdc mark

 

so first run made 110 at wheels not going over 5 k

 

on the road power was late and lacking.... after finding the boo boo it went back to make 125

 

 

 

don`t know the jet size as i was so worried that i had just finished building it the day before and i was stressed he was revin my baby

[SimonJ 2]

Mine up from 138 to 155 at the flywheel following 285 and carbs. Sounds about right I think?

[James_R 3]

Jim sounds pretty good

 

Simon - what was the engine before??

[dimmapalmer 0]

ive put my old 1.9 box without the limited slip and it pulls like a bastid now, maybe the box was holding it back? i have no idea.

going into corten miller sometime soon to let them have a fiddle.

 

need a decent exhaust now realy.

[SimonJ 2]

James,

Skip Brown fast road conversion before, giving the 138 at the flywheel. Lightened/balanced, head work and a mild cam, pulled well from 1000 in 5th. Should be a bit wilder now but haven't driven it yet.