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 Post subject: Re: Our little cultus racer
PostPosted: Tue Jul 09, 2019 6:51 pm 
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and if it was lean on the middle two how the F does that happen....after I changed the surge tank back to a standard tank setup I removed the fuel rail and tested all the injectors which all flowed exactly the same amount...there are no leaks around the inlet manifold...


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 Post subject: Re: Our little cultus racer
PostPosted: Wed Jul 10, 2019 8:57 am 
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Location: Cust
You're running on avgas?

That boat trailer looks a bit high, I guess enough speed and it'll work alright.


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 Post subject: Re: Our little cultus racer
PostPosted: Wed Jul 10, 2019 9:08 am 
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nope...98....has knock sensor and was miles away from the knock threshold done by Chris with knock ears on....


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 Post subject: Re: Our little cultus racer
PostPosted: Wed Jul 10, 2019 9:16 am 
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ok Sam you put me off the Hayabusa.

I might go with the other idea and rebuild the other motor in the donor car to STOCK. no fancy crank...no under drive pulley...no lightened flywheel...no fancy rods....no fancy pistons....just stock cultus cams....get rid of the hydraulic lifters....and stick a low boost turbo on it....aim for little more than 140 hp so it wont grenade....revs no higher than 7500....taller tyres and lower final drive on the dog box....That way I know the dog box will handle it and we will still go as quick...probably cheaper than rebuilding the current boat anchor for 100 more laps....

Are thugs eBay turbos any good for low boost?...and i do mean low....we already can go 3 secs faster than we need to. 1:25:00 is the time we want....so far it has gone 1:22:055 on semi slicks....

The stock motor will still benefit from the dog box...after all its just gear ratios.


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 Post subject: Re: Our little cultus racer
PostPosted: Wed Jul 10, 2019 1:39 pm 
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Location: Australia WA
Now you thinking straight =D>

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 Post subject: Re: Our little cultus racer
PostPosted: Wed Jul 10, 2019 3:05 pm 
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The best plugs for performance are Cooper plugs don't use iridium, just use bpr7es or colder now since you are going turbo


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 Post subject: Re: Our little cultus racer
PostPosted: Wed Jul 10, 2019 3:59 pm 
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haven't said Im going turbo yet....just that im not doing the NA rocket motor again....might just go stock on the gti motor in the donor car and put the cultus manifold on it....and the bits from the other engine to drive the link extreme....and maybe the three tech cams...then run it on our dog box...see how it goes.


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 Post subject: Re: Our little cultus racer
PostPosted: Wed Jul 10, 2019 4:24 pm 
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Location: Australia WA
No need to admit it, you've thought it through and looking for turbo, Vitara pistons etc already :)

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 Post subject: Re: Our little cultus racer
PostPosted: Wed Jul 10, 2019 10:31 pm 
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any news on the engine. did you run a harmonic balancer ?maybe a broken crank.


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 Post subject: Re: Our little cultus racer
PostPosted: Thu Jul 11, 2019 12:20 am 
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I used to run stock build, 10:1 compression with Mike's cams all day no probs. If u like the NA game you can go with the cultus pistons, stick to OEM clearances and you should be fine.


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 Post subject: Re: Our little cultus racer
PostPosted: Thu Jul 11, 2019 7:09 am 
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I guess it's fine to speculate but I wouldn't be making any decisions until you know the cause of death. There are a lot of 25 year old parts in these engines, some of which with hindsight are better replaced. It's absolutely possible to build a 130whp engine that will last for several seasons.

Personally I reckon you need to build your own engines. Find a good machinist and do the rest yourself. Most race engine builders won't know the first thing about G13B's or in most cases building NA engines. Pretty much every rally engine in NZ is turbo so that's their bread and butter.


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 Post subject: Re: Our little cultus racer
PostPosted: Thu Jul 11, 2019 8:35 am 
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Thanks for all the comments. I’m taking it out today. Then tomorrow it’s going to the builders.
Sam the people that built it have a long association with a g13b in an off-roader running the same power and revs.....up to 8 hours on enduros at a time....they refreshed it every few years. I think they have enough knowledge to build this one.
Know I don’t know the cause yet. I’m not pulling it down or being there because i have better things to do. either way I’m not rebuilding that engine....just want to find out what broke and not looking to apportion blame. I think if they did something wrong it would have shown up sooner.

At this stage we will freshen up the donor car engine and chuck it in to get back on track and take it from there.

With the electronic throttle and the dog box plus the very quick changes there was often a 400 to 500 rpm flare on the upshift....I am wondering if that was just too stressful on the engine happening at 8000 rpm. We know the throttle butterfly would not close fast enough....in fact 50 milliseconds after it was told too. The blip it gives us is totally awesome and I believe really saves the gearbox. Please don’t mention heel and toe....don’t wanna hear it. But it may have created a monster??? If it does it in the stock motor (which it may not as std flywheel, crank and pulley) then we will fuel cut it on the upshift and accept any backfiring (just cut fuel when clutch is pushed above 7000 rpm) and get the hyd lifters outta there.

I’ll report on the failure when I know.

Sam....I’m not building my own engine because I’m not a race engine builder....the first time I did it it ran a bearing.
But I might freshen the stock motor myself....I shouldn’t screw that up too bad.


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 Post subject: Re: Our little cultus racer
PostPosted: Thu Jul 11, 2019 11:19 am 
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A brief blip at 8500 shouldn't be enough to cause any problem. If you're logging rpm then you should be able to see whether it exceeds that.

Once it's been pulled down then you'll have a better idea whether it's been caused by fatigue, quality of parts, something foreign etc. You'll also know what's survived and can be reused.

Obviously one of the reasons for running avgas is the guaranteed fuel quality which you don't have with 98. Sounds like you can rule that out if the knock sensor hasn't recorded any detonation. That would suggest that the damage to the plug is from something metal in the pot be that a valve, part of a piston or something from the inlet.


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 Post subject: Re: Our little cultus racer
PostPosted: Thu Jul 11, 2019 5:17 pm 
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well its loaded for the builders in the am....no.2 has run REALLY lean.....did the injector fail?
soon find out.


Attachments:
File comment: boat anchor
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58451061590__FC467EC0-79BB-4B07-9361-256762C12030.JPG
58451061590__FC467EC0-79BB-4B07-9361-256762C12030.JPG [ 227.69 KiB | Viewed 4 times ]
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 Post subject: Re: Our little cultus racer
PostPosted: Thu Jul 11, 2019 8:12 pm 
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Location: Trinidad
For future, prob run an o2 sensor per runner


Last edited by ng357 on Fri Jul 12, 2019 6:13 am, edited 1 time in total.

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 Post subject: Re: Our little cultus racer
PostPosted: Fri Jul 12, 2019 5:26 am 
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From the photo it looks like two that are too rich and one that's lean. You said that it was running too rich according to the ecu yet you have one pot that seems to be too lean, that doesn't add up. You don't have any more form of Closed Loop Correction going on?


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 Post subject: Re: Our little cultus racer
PostPosted: Fri Jul 12, 2019 5:36 am 
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It was 5% rich throughout the range but that an average of the four cylinders so maybe some were overly rich compensating for the lean one. No closed loop correction and wouldn’t work anyway....would need four seperate lambda sensors and controllers.


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 Post subject: Re: Our little cultus racer
PostPosted: Fri Jul 12, 2019 7:15 am 
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My understanding is that CLL doesn't require 4 sensors to be configured, it can be set using one narrow or wideband sensor.

It looks suspiciously like foreign material from the failed surge pump has restricted the flow in one injector and the ecu fuel trim has corrected the overall ratio resulting in three rich pots and one melting pot.


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 Post subject: Re: Our little cultus racer
PostPosted: Fri Jul 12, 2019 9:53 am 
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so preliminary diagnosis has come in by way of a camera and sump removal.....now they are pulling the head.
no bearings run, no broken crank or rods, no broken valves. but a broken piston probably caused by the lean ness when I screwed up with the surge tank setup and also the lean runs when we had surge from the main tank and low fuel. Why only one piston? maybe because the operating environment was a little hotter in that cylinder or it was getting less gas than the others.

injectors clean as a whistle....no difference in flow.

so the camera shows part of the top of the piston missing...a small piece by the sounds of it....rattled up and down hitting the plug...and going back up into the inlet manifold..

Damn it...those pistons were not cheap.

so it seems like mechanical failure probably prompted by lean running. which I fully admit happened and also was caused by me...not once but twice.

The pistons when they arrived had a very very thin part to them by the inlet valves....Ill be interested to see if thats the piece thats missing. other than that...this engine did not need to grenade.

later today he will have the head off and the pistons out and a full report on the cause.


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 Post subject: Re: Our little cultus racer
PostPosted: Fri Jul 12, 2019 12:05 pm 
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No great surprise in terms of what's failed. It was really only a question as to what had melted.

I'm not so convinced about the cause of the lean running in #2. Looking at that extractor I'd have thought that it was running lean when it died and that it's not just the result of a previous problem. If it had run lean and was now running a similar mixture to the other cylinders then it would have lost that white coloring pretty quickly. It's entirely possible that running lean might crack the piston which would then fail at a later point but the color is what would concern me with that theory. I'd be having a close look at the injectors, the fuel feed and any possible air leaks.


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