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Mad Scientist

[engine_work] 2.2 Gti6 Engine Build

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Mad Scientist

I thought it was about time I started a project thread for something! Since the major job at the moment is my new engine, I thought it would be a good place to start.

 

I run a 1990 205gti that started life as a 1.9. For the last year, 2000 miles and some track time it has been running a 2.2 16v, built by myself. The original build was a bit of a "suck it and see" affair. I took advice from lots of people, and decided on the company to design and order the custom pistons, sort the head with some 3 angle valve seats and a skim and supply some other bits and bobs. These were the only things I did not check, since I put my trust and money in said company (who will not be named on here).

 

The car was mapped by Sandy, who did a great job (in hindsight its testament to his skill that the engine did not kill itself), but it never felt "right". During the mapping, Sandy commented that it wouldn't take the ignition he thought it should, but we shrugged it off and plodded on. He knew it wasn't right, but he mapped it as best as possible.

 

HOWEVER.................on a rolling road day in May, the car only made 191bhp, which was way down on what we expected. The owner of the rolling road also commented that it felt like it needed more ignition. Some detective work ensued.

 

I managed to get hold of the diagram for the pistons, and sussed the issue out pretty quick. The "designer" had put "+4" on the sheet in the required net volume section (including cutouts). He presumed this was a 4cc dish (thus adding to chamber volume) when in fact the manufacturer used the "+" sign to indicate a 4cc dome.

 

If you know how you calculate a compression ratio, you will know where this is going..........................

 

The "designer" also told me the combustion chambers in the head had been measured to be 36cc after a skim. This turned out to be innacurate too.

 

Net result was a compression ration of over 14.5:1, using a 282/275 degree inlet/exhaust cam. No wonder Sandy couldn't get the ignition in!

 

So..........................it was time to rip apart the block, trust noone (except Sandy!) and start over!

 

Nothing happened with the 205 for a few months whilst I rebuilt a 306 rallye, but thats gone now. Let battle commence!

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marksorrento205

Looking forward to keeping an eye on this thread Pedro. It will be top notch now your not messing with what sounds like cowboys. Looking forward to the passenger ride :D

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welshpug

thats quite a bit of compression!!

 

is the plan to just re-engineer the pistons till the compression is correct?

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pip470

At least its too much and skimming the pistons is an option. Also a head with a bit more volume in it would also bring that down. Im too looking forward to keeping an eye on your progress. What c/r are you aiming for?

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Anthony

Net result was a compression ration of over 14.5:1, using a 282/275 degree inlet/exhaust cam. No wonder Sandy couldn't get the ignition in!

Holy crap! An 8cc (plus whatever the head volume variance was) difference is quite some oversight, and in a way I'm quite surprised that it held together and didn't melt something with that sort of compression on (I'm assuming) standard pump fuel :o

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dcc

I am sure that now you know you're problem, you wont need any, but good luck!

Edited by dcc

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Mad Scientist

Good question............which leads me on........

 

(I would like this thread to be a bit of a resource for people that have not done much engine work, so whilst I will use technical terms and explanations, if you want to know what something means, please ask. I will either answer myself, or leave it to anyone else that wants to chip in.)

 

 

The old engine has been completely stripped now, and various parts have gone to various people for work. I like to do everything myself with engine building, but there are some tools I can't justify buying. Like boring/honing equipment, skimming equipment, flow benches, lathes, seat cutters, mills etc. Thus, the technical engineering work gets sent out to people I can trust. Usually they are close by so I can keep involved personally. There is a new exception to this rule though..............more info in a bit.

 

To answer your question Welshpug:

 

The pistons are JE 87mm items, and the last thing I wanted to do was spend more money on pistons, since these were not fit to be sold on in there current guise. On inspection and measuring, I worked out that machining them flat would remove approx 6 cc. This would leave a crown thickness of 5mm, which is OK. I would want at least 4mm crown thickness so there is scope for machining a small dish if needed to gain the extra cc I need. There is also room to deepen the valve reliefs. I think we should get them to -5cc without trouble.

 

The second part of this puzzle is the combustion chambers in the head. I had an unskimmed head that was suitable for the job. This is what went to the engineer that is not local. Mark Shillaber at SRD to be precise. I will detail the head work later, but Mark has enlarged the combustion chambers to 40cc.

 

For the benefit of some, this gives the new compression ratio as follows.

 

 

Compression ratio (CR) = Swept Volume + Clearance Volume/Clearance Volume

 

where swept volume is the capacity of one cylinder in cc and clearance volume is the cc of the head combustion chamber, plus compressed gasket volume, plus the volume of any piston dish (or negative if a dome) and valve cutouts.

 

Using 92mm stroke and 87mm bore, with a 1mm compressed 88mm Cometic gasket and pistons at deck height at TDC my CR will therefore =

 

546.909 + 40 + 6.08 + 5 / 40 + 6.08 + 5 = 597.989 / 51.08

 

= 11.7:1

 

This will be spot on for the cams, which will be the same as the original build. Catcams 4903110 (282 inlet, 275 exhaust, 11.5 max lift both, 2.95mm at TDC inlet, 2.45mm at TDC exhaust, 108 peak angle both).

 

Having the pistons flush with the deck at TDC and a 1mm gasket will also reduce squish, without getting too close for comfort.

Edited by Mad Scientist

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Mad Scientist

Video of the original engine on the NW rolling road day. This is where the "lightbulb" moment happened and I realised further investigation was needed. Those in attendance will tell you I really chucked the toys out of my pram!!

 

http://www.youtube.com/watch?v=x_cxyJPs40A

 

 

Anthony: You are completely correct, its a massive variance, and a complete joke considering where it had been done. Thank God for Sandys mapping or these pistons would not be fit for reuse! I always run on V power since this is a rally/track car and not a daily driver, but that can't have helped too much. Hell, I could just about have run diesel!!!

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Mad Scientist

So lets highlight the plans for this engine.

 

The car is going to be competing in the ANWCC (association of north west car clubs) tarmac rallying championship next year, so the focus is on real driveability. As a stage car it has to have good low and mid range. I could easily go for silly power at daft revs, but it would not suit the needs of the car. As a 2.2 we are already losers (!!!) as we will be up against mk2 Escorts with £25k engines, but the aim is to not come last, not to win.

 

I will be reusing some parts from the original build, adding to these with new and uprated items as follows:

 

Engine parts carried over from version 1:

 

87mm JE pistons (all be it re-engineered)

92mm stroke diesel crank

Alloy crank pulley

Standard S16 baffled sump (may add further baffle kit)

Windage tray

Catcams 4903110

Piper double valve springs

Piper valve spring retainers

Colin Satchell/Sandy Brown inlet manifold using GSXR 44mm throttle bodies, running 4 omega v6 bosch injectors and 4 106 gti pecos.

 

New engine parts for version 2:

 

Fully worked SRD head, with 0.5mm bigger single piece stainless valves

88mm Cometic 1mm head gasket

Replacement GTI6 block to enable nice fresh bores and deck

Custom Robson conrods to suit deck height of block, compression height of pistons, 92mm stroke and width of diesel crank big end journal

Rebuilt oil pump

Rich W lightweight billet flywheel

Custon 4-2-1 exhaust manifold to match engine/exhaust cam: To be made by JP Exhausts, Macclesfield.

Remap by the good man himself: Sandy Brown

 

Whilst the engine is out, I will also be fitting a weld in strut brace from Colin Satchell, seam welding the subframe mounting points, and adding a brace between the engine mount and strut tower. I will also be tidying up the look with some more shrink wrap, and replacing the connectors on the peco injectors for quick release junior timer connectors. The bay will then get a fresh lick of white paint.

 

I will also be fitting a Mocal 13 row oil cooler infront of the rad, with provision to blank it off (most of the time) with a carbon panel.

 

Further new additions:

 

TranX diff (come on Miles, wheres that quote!!!!!)

Xsara VTS box to replace 1.6 BE3 previously in place

Whatever I can think of and afford!!!

 

 

 

Any thought on the spec. welcomed.

Edited by Mad Scientist

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Henry Yorke

That explains why you were a miserable fart afterwards at the pub!

 

A techy question from a non-techy: With the domed pistons and the high compression and high lift cam, I'm surprised the valves didn't meet the pistons. Were the cut outs really that deep or did something else save you?

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welshpug

the dome is across the middle of the piston hence clearing the valves :)

 

Do you have a projected power/torque area for it? Any particular reason to be going into the 2000cc + class rather than sticking to the up to 2.0? I know the rallies I have been to of late around the south it doesnt make a big difference though with the money spent on the 2.0 escorts!

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Mad Scientist

The valve reliefs were the only part of the piston designed properly!

 

They are of sufficient depth and diameter to avoid valve contact, and are also machined into the piston at the same angle as the valves.

 

Although I did not check the compression ratio, I did "dummy build" the engine. This involves assembling the engine enough to check there is sufficient clearance between the valves and the pistons, and also between the valves and the edge of the valve reliefs.

 

This is done by bringing the piston to TDC (top dead centre) and, using a dial gauge indicator, measuring the distance between the valve when fully seated and the piston. This is checked on both an inlet and exhaust valve. Take away the valve lift at TDC and it leaves you with the clearance. For safety (and also because the pistons are actually slightly closer to the valves 6 degrees after TDC) there must be 2.5mm clearance on the inlets and 3mm on the exhaust. Some people run less, but you pay your money, you take your chance.

The way I check that the valve has enough clearance between the valve head and the cutout is by placing a piece of plasticine in the cutout, assembling the engine as necessary, and pushing the valve into the plasticine. Once its dismantled, you can measure the clearance. I had 2mm, but will have 1.5mm with the new larger valves.

 

With these pistons and the 1mm gasket, I actually have enough "room" to run up to 4.75mm lift on the inlet at TDC and 3.75mm lift on the exhaust at TDC.

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Mad Scientist

the dome is across the middle of the piston hence clearing the valves :)

 

Do you have a projected power/torque area for it? Any particular reason to be going into the 2000cc + class rather than sticking to the up to 2.0? I know the rallies I have been to of late around the south it doesnt make a big difference though with the money spent on the 2.0 escorts!

 

 

I am aiming for around the 230+bhp mark, and high 100's lb/ft. Looking at similar builds past and present, this should be achievable. The only "restrictions" are the 44mm bodies and the cams, so it may well get upgraded at a later date.

 

The reason I am sticking to the over 2 litre class is there are fewer entries in this class. I'd rather come last out of 10 entries than mid-table of 40! Like you say, theres enough money in the up to 2 litre class to prevent me needing a bigger trophy cabinet anyway!

 

I could just go in the up to 2 litre class with a 2.2, like most of the mk2 Pintos, but I have morals......................and a public project thread now too!!!!

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Mad Scientist

Lightweight billet flywheel just landed! Can't believe the difference over the standard item.

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thelegendofando

Good work! Glad to see you have a project thread! :D

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Miles

I think I replied to this, just the last week I;ve had gearbox's coming out of my .......... ........ :lol:

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Mad Scientist

You didn't mate! Could you PM me a price to strip, clean and check a xsara vts box, fit a tran x, and courier it back. Cheers Miles.

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Jarrus

Looks like a good project mate,

 

Sorry to hear about the incompetance of the engine people before hand, 14.7:1 compression is kind of Methanol fuel compression ratios! as daft as its sounds, it would have been good to see what the engine would ahve done running on Meths with some more mapping, anyways I'm waffling and I suppose it's pointless saying....

 

I wish you good luck in your new endevours and I hope you do well in rallying.

 

I'll be keeping an eye out for this one...

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Mad Scientist

The head should be back tomorrow, so I'll be able to get some pictures up. I also now have my acl duraglide 780 mains and big ends.

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Mad Scientist

Possible change of direction here. Looks like the satchell gsxr bodies set up, complete with injectors, fuel rail and tps and the catcams 4903110s with springs and retainers may be for sale...........let me know if you're interested

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welshpug

definitely!

 

any particular reason?

Edited by welshpug
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marksorrento205

Bigger and better I would think ;)

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Mad Scientist

Haha!

 

It seems a shame to not make the most of what I've got here. The all steel bottom end will be bullet proof, and Mark Shillaber has gone to town on the head.

Unfortunately, the limit of the bodies is probably 240bhp, and I will need race cams and solid lifters.

 

In for a penny........!

 

Will be after around £500 for the bodies.

Set up includes 4 Bosch blues in standard rail, 4 106 gti pecos in the outer bike rail, pipercross filter, tps with connector, gsxr bodies with modified throttle cam, and trumpets.

Around the same for the billet catcams, catcams springs and catcams retainers.

 

:)

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welshpug

nice, thought that may be the case, guess 42's can only get you so far!

 

do you do installments? :lol: would love the bodies, got an ecu and mild cams ready :D

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Mad Scientist

They are 44mm gsxr k5 bodies. I have already told sorrentomark by text. Payment plans are no problem! 200% apr!

 

Go on Welshpug! You know it makes sense!

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