[engine_work] 2.1 S16 Build Diary

[DrSarty 90 1 Cars]

What's happening with this Doof?

[Doof 11]

Wow, it's been a while since i've been on here. I've been trying to blank this whole thing out of my mind for a long time as it was just turning out to be such a ball ache. I'm making progress again after consulting Sandy, making mistakes, consulting Sandy some more and making more mistakes.

 

Basically I was struggling with the tapping sound and the low compression on one cylinder so i bit the bullet and took the head off. No majors there, all looked reasonable. I went mentioned to Sandy at some point that I had used a standard GTi-6 head gasket (mistake number 1) as I was told (Clicky) that it was ok, this turned out to be a bad idea as I suspect the pistons were just coming up and tapping into the edge of the gasket. I guess this is the problem with believing everything you read on the 'net.

 

I took a look at the head and in the end bit another bullet and just sent the head to Sandy for him to measure everything up and do whatever was required to get it back to perfect condition. This turned out to have 5 bent valves! I don't know how it got 5 bent, i'd have expected an even number to be honest, perhaps some were bent before I got it and perhaps I bent some when assembling it. Other than the bent valves it seemed ok, hydraulic lifters seemed good but were given a once over and a skim.

 

I got the head back and all was going well, until i dropped the damn thing, well not really a drop, but it came to rest on it's valves with the cams in and I just wasn't happy hoping it was alright, so the valves came out again and went for a check up, they seemed alright but were reground again just to be sure. I got the valves back fairly recently and put them back in along with the cams (after having them polished as one of the lobes somehow got a damn scratch in it!!) and was about to put the head on...all was going well, i was over the moon that progress was being made...and then I noticed something. How come I can see daylight through the inlet ports? On all cylinders? Oh s*it, here we go again...it turns out that after refacing the valves and lifters etc i've now ran out of travel on my lifters so they valves never fully close!! The valves are currently on their way to Sandy who is going to skim a bit off the top of the valves and then i'm really hoping I can put it together for the last time and run it up.

 

I really am confident this time that all will be ok. I feel like i know it all far too well. I've been through pain, sweat, tears and more pain with this thing but it WILL be worth it. And i WILL finish it!!!

 

Hope all is well with everyone on here, not been on much as i've just been trying to forget about it all. Hopefully in a few weeks time I'll head it fire up again with a nice quiet hummm...time will tell.

[Sandy 189]

I REALLY hope so too!

[Doof 11]

FINALLY, some good news with this project. I finally found the cause of the tapping, and this time i'm certain of the problem so when assembling it i was really confident. I sent a lifter and valve spring / valve down to sandy to check it all out and he noticed that I was using standard lifters on non standard spring caps!! It turns out that the lifters were actually pressing on the spring cap before they actually hit the top of the valve stem. I think the lifter would push down by about 1mm before it came into contact with the valve...as you can imagine, 16 of them doing that would cause quite a noise!

 

I ditched the double valve springs and just went back to some new standard valves and they work nicely with the standard lifters and spring caps. In fact, i just finished building it last weekend and it fired up again sounding much much nicer!!!

 

Back to tuning the megasquirt system. I took it for a drive the other day but really need to head out with another person so i can tune on the fly.

 

Will post back with videos and progress on the tuning

[petert 550]

Good work. I'm glad you've got it sorted. The standard valve springs are actually very good, provided you stay within their limits. Many think they're average just because they're the standard spring. But PSA really did their homework, and provided the seat pressure is set correctly and cam lift is less than approx. 0.425", they will work almost forever.

[Doof 11]

Still going slowly with this project. I'm hopefully going to be sorting the binding brakes in the next week or so.

 

Another problem I seem to have is that since taking the head off and rebuilding it, my idle MAP value has gone from around 45kpa to 75kpa. When driving now on part throttle I seem to have around 95kpa which is just crazy. What could cause this problem? I know the MAP sensor is ok because it shows around 100kpa when the engine isn't running....

 

Can an air leak really cause it to be that high?? And why does the engine not accelerate like mad at 95kpa when cruising! COnsidering it's running rich too!

[Doof 11]

Anyone got any thoughts on this high idle kpa? I've got it running (somewhat badly) at the minute and I just can't get an idle kpa lower than about 70-75.

 

I'm pretty fed up of making no progress with this tuning malarky, i thought it might be slightly easier than it's proving to be!

[welshpug 1,622]

have you checked cam timing?

[Doof 11]

No, I've not tested it. Can the cam timing really throw the idle kpa out by that much? I've a feeling i didn't do it as accurately as the first time but if it's good enough to run...

[welshpug 1,622]

not sure myself, never delved this deep into engine tuning myself.

 

doesn't a higher figure mean more vacuum not less?

[Doof 11]

Right, i decided to check the cam timing today and I'm glad I did!

 

At TDC I had:

 

3.35mm lift on Inlet

1.75mm lift on Exhaust

 

Now, I think that's way too much, certainly on the inlet. Does anyone know if this could have cause the valves to clip? I just did a compression test with a bit of lift taken off both and got around 190psi on each. I was hoping for 200+ to be honest as I'm sure that's what I had before.

 

I'm wondering if the verniers have slipped because i never set the values to the above!

 

Got a guy coming round tomorrow who knows Megasquirt so fingers crossed (if i dont have more bent valves!!!) then I might get it running ok tomorrow!

[DrSarty 90 1 Cars]

At TDC I had:

 

3.35mm lift on Inlet

1.75mm lift on Exhaust

 

Now, I think that's way too much, certainly on the inlet.

 

I'm no cam expert, but PeterT recommends ~2.25mm lift on his stage II inlet at TDC, so at a guess I'd agree with you.

[Doof 11]

Ok so 3.35 was high but hopefully not too high as to clip valves.

 

I'm panicking that 190psi compression just isn't enough and i've got bent valves again...I'm sure i tested it before and had 240psi. Gulp.

Edited September 11, 2010 by Doof

[DrSarty 90 1 Cars]

190psi does seem low.

 

If you need more valves, I have a set of 16 which appear all good. £4 each (£6+ new) or £55 the lot posted.

[Doof 11]

I don't think you understand...if i need more valves...there'll be another for sale post like yours!

[Sandy 189]

Time it correctly and re-check the compression.

[Tom Fenton 1,525]

As above. We once took the twin cam Mini to the rolling road to play with cam timing to see if there was any benefit to be had in terms of it coming onto boost earlier, or more power etc.

 

We found about 20bhp on the rollers at the top end, but the consequence was that the next time we tried to fire it up cold it simply refused point blank to have it. Put the cam timing back where it was and normal service was resumed.

[Doof 11]

The problem is, I did the compression test after adjusting the timing and it was 190psi...

 

It just doesn't seem high enough to me, i'm wondering whether to start pulling it apart today. Could have it done today and ready to send away for checking...

[petert 550]

190+ psi seems perfectly normal with that inlet cam in the right position. A bigger cam again would have even less cranking pressure. If advanced (more lift @ TDC) it would have more than 190, as the compression stroke doesn't start until the inlet valve closes. I'd be driving it. It won't have a bent or leaking valves with that much compression.

[Doof 11]

Really? Even on an engine with 11:1 compression ratio? (not actually sure how that would affect it). I swear it was 240psi with the incorrect timing. It seems crazy that you can lose 50psi with just 5 degrees or so advance / retard.

 

I almost wish I had a spare MI head so i could see how close valves would be with 3.35mm and 1.75mm lift at TDC... Do you know roughly how far you have to go before they clip peter?

Edited September 12, 2010 by Doof

[Doof 11]

Just found an old post of mine and after putting fresh valves in i was getting 250psi on a compression test...I've lost 60psi somewhere!

 

Can anyone who know's Mi heads say whether 3.35mm inlet and 1.75mm exhaust lift at TDC would clip the valves? As you can tell, i'm worried about the loss of 60psi

[petert 550]

There's only one way to find out! Put it back around to 3mm and measure the comp. again.

[Doof 11]

Ok,time to just drive the thing. I took it for the MOT to other day and it passed thankfully! That and I did another compression test and got 225+ on each cylinder!

 

Finally I'm happy that it's put together properly and is ready for a good run and an RR session. I'm still struggling with idle etc but I figure I'll get it tuned for general driving and then come back to idle. For now, i think it just needs some miles on it ready for an RR session with Sandy.

 

it feels nice and pokey and sounds pretty good too. I'm also pleased that the suspension hasn't seized up and the brakes feel amazing with the 406 MC!!

 

The only issue I'm confused about is a wavering AFR reading at cruise. Something is causing the pulse width / duty cycle to change resulting in a wavering AFR...but oddly the car cruises along just fine. I'm going to investigate any more exhaust leaks but I dont think i've got any!

 

I'll try and get a video up soon...hoping to pay Sandy a visit for the RR session in a couple of weeks if he can fit it in, then i'll finally have some numbers to see how it's done. Come on 200+ bhp!

[Vili 17]

The only issue I'm confused about is a wavering AFR reading at cruise. Something is causing the pulse width / duty cycle to change resulting in a wavering AFR...but oddly the car cruises along just fine. I'm going to investigate any more exhaust leaks but I dont think i've got any!

 

I'm not sure what is the spec of the car, but are you sure that your fuel pressure stays steady? My 306 S16 had some fuelling problems. The fuel pressure didn't stay steady because of broken pressure regulator. I chanced it to an used original and it was also "out of tune". By that I mean that the pressure was 2.4 bar vacuumpipe disconnected instead of the 3.0bar. There might be some quality issues with pressure regulators used in S16. (Or for some reason they don't last in 306. The 306 fuel pump has a tendency to suck air when tank is less than 1/4 full.)

Broken regulator could be causing the wavering AFR readings via the lambda correction.

[Doof 11]

The thing is, the pulse width and duty cycle are definitely changing so for some reason the ECU is deciding to add more fuel. This makes the thing the FPR is alright...