7 port ignition mapping issue.
Turbo Mini Forums

Sorry none turbo related issue. I recently mapped my 7 port 1330 n/a engine spec

Webcon modified head, 36x29
11-1 CR
286 cam
1.5 rockers

After calibrating my fuel pulse width's at a safe ignition I did some power runs. I was very disappointed to only pull 51 bhp ATW's at 6500 revs with 25 advance.

I then found 75 bhp ATW's with 36 degrees.

But to my amazement found peak power at 47 degrees BTDC at 98 bhp ATW

I straight away assumed, sensor postion, or I marked TDC wrong. Tonight ive double check with timing gun and them removed head to check, but everything is spot on.

Why does it require so much?

I've also lost 3 Bhp by fitting 1.5 Rockers.??
I also found 20 ft/lb torque at 3k by adjusting tappets from 15thou to 18thou.

I'm petty confused, and can't understand Wots going on.

Edited by alaskanow0 on 1st Sep, 2012.

Class C 3rd Place Avon 2011 14.18 @101mph

compression wrong ? cam timing wrong ?

And are you 100% sure the ignition timing is what you think it is ?

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

This 7 Port setup is currently giving me a increase of 12bhp over a nice stage 4 head with Hif44, aldon dizzy at 34 degrees.

It only shows more power from 4k, but excel after 5k.

Class C 3rd Place Avon 2011 14.18 @101mph

That much timing would suggest to me that the static CR is very low. Certainly not 11:1. How sure are you on your various volumes? Did you measure them yourself to be 100% sure?

I'm 100% sure on CR, TDC and sensor position. I double checked them several times. The problem seems to be linked to the alloy head.

Do you think I need to increase to 12-1CR, as recommended by professional engine builder friend.

Edited by alaskanow0 on 30th Aug, 2012.

Class C 3rd Place Avon 2011 14.18 @101mph

whats the deck height and plug arangement? the plugs arent down holes like the mini sport heads are they?

Ive already increase CR from 10.6 to 11-1, by skimming the head, but not really gain any more power.

Class C 3rd Place Avon 2011 14.18 @101mph

Deck height is 0.5cc, piston is vitually level with deck. The chambers have been modified to allow spark plug to be more prominent in the combustion chamber.

Edited by alaskanow0 on 30th Aug, 2012.

Class C 3rd Place Avon 2011 14.18 @101mph

I'm wondering about cam timing now. I moved it from 108 to 106 degrees to compensated for 1.5 Rockers and to move torque curve slightly down the rev range.

Class C 3rd Place Avon 2011 14.18 @101mph

Pistons have 8.2cc
Deck height 0.5cc
Bk450 3.8cc
Head 20.2cc
Ring land 0.5cc


11.05 / 1 ???

Class C 3rd Place Avon 2011 14.18 @101mph

on a 1330 yeah.

Yes 1330.

Class C 3rd Place Avon 2011 14.18 @101mph

have you made a mark at tdc on the pulley and a coresponding mark on the case ,that you are sure IS tdc ,and using a strobe on those marks ?

(oops sorry didn't read your post properly , i see you have done this .)

also,are you getting a waste spark induced double reading so your 47 degrees is really 23.5 degrees . ?

my digital strobe usually reads double .

Edited by robert on 31st Aug, 2012.

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

Yes my strobe does read double, due to wasted spark. I've taken this into account. My laptop shows 20 at idle, which reads 40 on timing gun.

Some information on the Internet suggest spark plug position as a massive effect on burn rate.

The sparks are my biggest bug bare, with the head anyway. They are tiny 8mm thread, with small tip, there are near on impossible to remove with the TB's. in place.

The plug gap is alot smaller than a standard ngk bpr7es. I did increase them slightly, hem...?

Class C 3rd Place Avon 2011 14.18 @101mph

Why did you have cam at 108 degrees? A 286 should be at 106 anyway, and why would you need to compensate for 1.5 rockers?
Now you have the 1.5 rockers check your springs have 40+ thou between the coils at full lift, this could explain picking up power by increasing rocker clearances

I seriously doubt it!

Sorry cam is a SW10, Swiftune's version of 286, was told 108 by them. I was hoping to tame it down slightly, especially as fitting 1.5's.

I will check spring Clearance, springs do look well compressed at full lift.

Edited by alaskanow0 on 31st Aug, 2012.

Class C 3rd Place Avon 2011 14.18 @101mph

Id put the timing back to 108 then otherwise your injecting the fuel with the valve in the wrong place

I seriously doubt it!

can you put the timing in the ecu to 0 and see if it lines up with the tdc mark at all?

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

if you do a compression check with a guage ,what do you get ?

and can you put up your ignition map here ? i'm wondering if there is some vacuum advance related thingy.

Edited by robert on 31st Aug, 2012.

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

I'll have a go, but whilst I've got the head off again am going to check valve spring rates and heights.

I also want to bench flow the head again, just to confirm flow rates at higher lift. I remember during development we began to lose flow after .380 lift. I thought we sorted it with more work to the throats. Maybe not?

I not prepared to give up on this setup yet, but all this time, money and hassle for a extra 12bhp.

Class C 3rd Place Avon 2011 14.18 @101mph

I will stick up my ignition map shortly. It's TPS v RPM only, no map compensation. I haven't managed to do a compression test due to size of spark plug hole, but no sign of head gasket failure.

Class C 3rd Place Avon 2011 14.18 @101mph

Cam timing being not as specified will lose horsepower. Get that right, check fitted valve spring height and check for binding at full lift with 16 thou clearances.
Im a bit confused that you have gone to lots of expense and effort then altered the cam timing to tame it down after fitting the 1.5 rockers.
TBH, I cant see that you will achieve massive gains with 7 port over a good 5 port but keep persevering and let us know how you get on

I seriously doubt it!

I've fitted 1.5 offset rockers from MED, as the valves are offset. I couldn't get hold of any 1.3's offset. I was adviced to advance cam timing to 106 by few people. I understood a may lose a few hp at top end but gain bottom end. This a road car and spends 95% below 5k.

Class C 3rd Place Avon 2011 14.18 @101mph

And yes, I have come to realise this isnt really a suitable road head, but for now I just want to get the best out of it, before I probibly move back to 5 ports.

If this means swapping the timing back to 108, more head work, different springs etc. so be it.

Class C 3rd Place Avon 2011 14.18 @101mph

Oh, dont get me wrong, the 7 port should make a better road engine than 5 port, Im just making the point that getting the mechanicals right before setting up ign and FI needs to be done and that you seem a bit dissappointed by only a 12hp increase when its a pretty good achievement on a mild engine spec.
I wouldnt give up on it either. Perhaps give Swifty a ring about cam timing, but if his cam is designed to operate at 108 it wont be optimal at 106 so the valves will be in the wrong places when the fuel and the spark are firing and no amount of fettle will get it right

I seriously doubt it!