john banks

A few thoughts are coming together in my mind from hunting down some of Quirt Crawford's comments in his forums, which I have tried to summarise my understanding of below.

He thinks that the first issue is detonation.

Second issue is hot spots in the cylinder head related to localised boiling, once this happens a vicious circle gets setup up where there is air instead of water and it gets hotter and hotter leading to local head warpage (presumably temporary) and a gasket leak. He recommends a stronger rad cap to increase the boiling point. Also recommends upgrading the cooling if the gauge temperatures are too high.

In another thread he also wouldn't recommend a compression ratio for running 1.7 bar on pump gas (93 PON equiv to Optimax approx).

My failures (including the piston failure) happened at 1.7 bar on similar octane, plus methanol and/or NF, at 8.7 or 8.0 compression ratio (piston failure at 8.7). There was light detonation whilst setting up but at the cylinder pressures involved with a lot of advance it could have been damaging I think.

Additionally the failures occurred during sustained very high speed usage, which would back up the hot spot theory. I was running 1.1 bar rad cap throughout, but now have 1.3 bar.

I wonder if the gaskets clamping and piston being a little structurally weak on the EJ257 were exploited by my overenthusiastic ignition timing, excessive localised coolant temperatures (some crack or warp heads here), working turbos that are struggling for flow a little hard. I have noticed other sources mention headgasket failures in a variety of engines without detonation just from going too far on ignition timing and hence cylinder pressure.

Quirt also recommended an 8000 RPM limit (with the right valvetrain which I have) on the stock EJ257.

So my new experiment will be to try cautious timing, 11:1 AFR and 20-22 PSI held to 8000 RPM on my EJ257 with (soon) a GT30R-12 rotated mount. I wonder if it will get near 500 BHP and hold together? I've asked Quirt for recommened limits for EGT and coolant temperatures.

I'm not worried about the pistons seizing in the bores really, but that will remain to be seen.

I think I am working around an inherently weak engine design, and hope it lets go gracefully if it does. I thought I'd give it another fling before going on to a closed deck block and forged internals if it fails.

Please discuss.

johnfelstead

which way round does the coolant flow John? does it go engine block>heads>radiator or radiator>heads>engine block?

Road car engines tend to cool in the former direction, race engines cool in the later. If it is the former i would try removing the water pump impellor and plumbing an electric water pump in the system, running it to cool the heads before the block and using a variable speed controler and no thermostat to maintain the required temperature.

You may also be able to drill the heads through into the water jacket where it is blanked if there is enough material available to remove steam pockets. It's been a while since i looked at the heads/block off so cant remember how well the coolant pasages line up.

john banks

Thanks for the ideas John, I'll look into it.

john banks

Post on NASIOC... are we?

"Regarding headgaskets, are you guys adding the additional steel dowels to the bottom two corners of the blocks ( where the head bolt holes are, basically matching it to the top two corners) to help prevent head shifting? I know that cylinder 2/4 side of the block already has the holes machined out to accept the factory dowels (about $5 apiece), whereas the cyl 1/3 side requires some drilling to get the dowels to fit."

David_Wallis

nope.

I cant see temporary warping of the heads personally.

Which turbo you using??

David

john banks

Andy's old one.

john banks

My heads seemed to be flat when measured with a straight edge and a feeler gauge. Is there a posher way to do it or should this establish that they are flat enough?

Is it fair to assume that running low-mid 400s BHP for 5000 miles if the heads were warped would have already caused a further leak?

CustomScoobyIOM

An interesting yet slightly sounds unbelievable issue from the states here.

http://www.rxauto.net/

Courtesy of the Google Ads

David_Wallis

I would expect so, but then the gasket will take 'some' irregularities (sp)

Its how Id check them john!

David

xephyr

Using the dowels doesn't prevent headgasket failure from head warping, but from the possible shifts a head might make laterally (parallel to the head surface). I used to have the problem with headgaskets on #4 cylinder, but this quick and easy fix solved it. I learned of this trick back in the day from Marcus at MRT and Jaime at Rigoli/ESX. The dowels are cheap, and can easily be tapped in using a hard piece of wood and a hammer.
Back before the 257 block came out, I was messing with the open deck 2.5, which was really sensitive to headgasket failure. The dowel trick was really helpful with those situations.

carlos_hiraoka

John do WRC engine's use electric water pumps ? ..... I thought that only track-oriented cars used such electric water pumps.

Carlos H.

Pavlo

the coolant flows bottom of block, ex side of heads, inlet side of heads, top of block, radiator.

johnfelstead

thanks Paul. Not a lot you can do then in terms of improving direction of flow then.

No WRC cars dont use electric water pumps, the FIA regulations dont permit there use, you have to use the OEM water pump assembly. Ford and then Peugeot have been excluded from events at post event scrutineering for changing components in the water pumps.

Prodrive chose to use two electric water pumps on their FIA GT Ferrari, we run two on the Esprit 6litre V8 race car i help with.

carlos_hiraoka

What's the advantage of running an electric water pump, also how is it controlled (via a ECU ?) and finally how much power does it take ..... ?

Carlos H.

johnfelstead

main advantages are you can do away with the thermostat and use the pump at a slow speed until upto the required temperature, then alter the speed to control your ideal temperature. The flow rate isnt dependant on rpm and you dont suffer any cavitation issues if the engine is used at high rpm for sustained periods of time.

You can either use the ECU to switch the pump on/off at set temperatures, or use a speed controller linked into the water temp to control the water flow more eficiently.

http://www.daviescraig.com.au/main/display.asp?pid=8

carlos_hiraoka

Have read about Prodrive using it on the Ferrari, and read quite a few impressive reviews ..... I am going to be competing on an endurance series this year with my STi ver. 4 (2L 350hp engine spec), so have been looking at this option just for safety. Will drop u an emai to ask u further details .

Thanx.

Carlos H.

Tim W

iTrader: (1)

John, was that 8k rev limit on a completely stock EJ257 with the standard Hyperutectic pistons?

john banks

Astonishingly, yes

Think I might do 1.5 bar at 7500 instead

Tim W

iTrader: (1)

Oh this could get very interesting Everything on my engine bar the EJ257 short engine (stock except for overbore to give 1 thou clearance on each piston) was speced to be good for 8k rpm

Mr J

John it good that you do the destruction derby, so we now what the limits is with phase2 heads when not running the turbo to edge

They have put some sick power on stock Ej257 over there...
thinking about Jeff that were running 1.65Bar to +8300rpm...but his piston gave up etc and Kingpin etc

Mine is holding togetherr so far, and think my Mistu/garrett hybrid it have pretty similar wheel(GT30R) as your Ion turbo, although icy roads it impossibel to map it over 1.2bar


Jan

P20SPD

iTrader: (1)

Mine was running at 7500rpm limit with stock UK phase 2 heads, with the the GT30R holding upto 1.6bar to the redline, and occasionaly off the limiter in 6th.

P20SPD

iTrader: (1)

albeit with uprated internals

Heads, and pistons (barring for the coking up) were fine when it was stripped down

Mr J

But your Hg went to right Steven ..

think is't no good idea to run the Impreza @ high speed for long time....
could it have been a factor ?


Jan

P20SPD

iTrader: (1)

Jan, we are still not convinced on the head gasket side, as cord couldnt see any issues with the gasket, which is slightly confusing.

Holding a car at its limiter in top is a bit stupid, but i didnt do it for long.

Tim W

iTrader: (1)

Steven, what expansion tank cap were you running? Stock or uprated?

john banks

I think the top speed runs killed mine.

Thinking of an EGT probe with a trigger to pull the scramble line on the AVC-R to drop the boost if EGT levels go too high.

If I keep it rich and am not running the turbo's nuts off with methanol, I will be able to keep the timing a bit retarded without hopefully excessive EGTs. So, keeping it cool and avoiding pressure spikes will hopefully show if it can live with high power.

Steven said he was running 1.1 bar cap in a recent email.

Steven, how high did your EGTs go?

Tim W

iTrader: (1)

I very much doubt that I'll need or want to run 1.5 bar (the maximum that I think will be necessary) to the limiter so I'm sure that will help with prolonging things. Mind you with the mileage it's likely to cover each year it'll probably last 2 or 3 before I get enough on it to be concerned

Made some serious progress towards getting on again with putting the car back together over the weekend...cleared out my garage down at my folks, there's more than enough room to get the Scoob in there now...if I relegate the Alpine to being outside the work area in the rather exposed tractor shed

Mark A

iTrader: (1)

What Apline have you got Tim. My friend is a massive Alpine nut, currently has a GTA, he's been racing a Renault 8 gordini till last year and has been looking for a A110 to replace it.

Mark

R19KET

Mark,

That's quite funny. I think Tim's referring to the "original" Sunbeam Alpine. Think it's a Sunbeam ?

Mark.

P20SPD

iTrader: (1)

John, whilst mapping we got over 1200degress c on the 1st run, 7000 rpm in 6th, but that came down to somewhere near 1050 on the top speed run at TOTB3 (after 3 consequtive 1/4's).

Highest egts on road, were 1100, which was in association with the limiter in 6th scenario.

Rad cap, standard 1.1 bar as John says, that was next on list to be changed.