Whoops!

[NitroDann]

You have 225rwhp, lets say 250 crank hp, although that is on the small side of estimates.

If you have 4x 440cc injectors on a 250hp turbocharged car any one of the various calculators online will tell you that you are at LEAST 90% duty cycle, assuming your fuel pump was healthy and you were running a fairly normal AFR.

Dann

[davekmoore]

So on a hot day they'd be over 100% and unable to supply enough fuel so it was running too lean hence the pinging heard by onlookers as it went up the hill to turn 3?

[NitroDann]

Possibly.

I mean you need to log AFRs to be sure but you were pushing your luck at that HP with those injectors thats for sure.


Dann

[davekmoore]

Ok then Dann, what size injectors should go in the rebuild, including some allowance for later adding some gentle work on the heads/cams and what you would describe as a proper turbo/downpipe/headers?

[bear2230]

Deatschwerks 700cc injectors
http://www.flyinmiata.com/index.php?dep ... r=04-41008

Might as well go for the 1000cc though Dave.
http://www.flyinmiata.com/index.php?dep ... r=04-41025

Im using the Deatschwerks 600cc injectors.

Richard.

[gslender]

Just remember that large injectors make it harder to start and idle smoothly. So go big, but set your expectations around that! If race car, then do it!

[davekmoore]

After a bit of further research I can see how the 440 injectors would be a restriction and would be leaning out the AFR as they were beyond 80% duty cycle. If 60% is optimum then it may need 1000s rather than 750s to be on the safe side. Will these also require a bigger fuel pump and/or anything else to flow more fuel?

Will the Haltech Interceptor cope with such changes?

How bad will starting and idling be?

How much worse than the present 8.5L per 10kms will it be on the road (don't care how much worse it'll go than 28.5L on the track!).

[bear2230]

How much worse than the present 8.5L per 10kms will it be on the road (don't care how much worse it'll go than 28.5L on the track!).

I reckon no better than 12L per 100kms. You will use more fuel but it will be at the right mixture so you won't blow your engine up again. (Hopefully) So thats good…...

[Sean]

After a bit of further research I can see how the 440 injectors would be a restriction and would be leaning out the AFR as they were beyond 80% duty cycle. If 60% is optimum then it may need 1000s rather than 750s to be on the safe side. Will these also require a bigger fuel pump and/or anything else to flow more fuel?

Will the Haltech Interceptor cope with such changes?

How bad will starting and idling be?

How much worse than the present 8.5L per 10kms will it be on the road (don't care how much worse it'll go than 28.5L on the track!).

Starting and idling with high CC injectors isn't as bad as lots of people who haven't tried it like to suggest. Lots of it also comes from teh old days where injectors were expensive so people were fitting (cheap) big secondhand rotary injectors with spray patterns that didn't suit the manifold and injection system of the engines they were fitting them to at idle conditions. Sure even the newest greatest, clean flow pattern injectors may not give factory perfect idle, but if tuned properly it also wont idle rough like a Harley.

I've seen LOTS of 4cyl 2 litre engines tuned with 850 and 1000cc injectors that would pass as factory idle quality to most people.

I've also seen two of those engines pass IM240 running on low resolution microtech MT8 ECUs on 98octane (i.e. not eflex).

The big problem is usually with a low res ECU where the injector time is not granular enough, so moving the idle values just one setting point would move from rich to lean and idle it up and down.

Depending on your ECU and set-up there are a few ways a good tuner can get around these.

[gslender]

All I will say is "dead time".... Get it right and large injectors can work fine. Get it wrong and good luck trying to get stable AFRs at idle. Does the interceptor let you adjust dead times either per injector or as a set?

G

[davekmoore]

Does the interceptor let you adjust dead times either per injector or as a set?

G

Any Haltech experts out there to answer this?

[gslender]

This thread kinda suggests you'd be pushing it to get it to work correctly... 5th injector... yuk!

http://forums.haltech.com/viewtopic.php?f=12&t=4431

...sell the Interceptor and buy an MS3 Pro and be gangsta !

G

[Sean]

Does the interceptor let you adjust dead times either per injector or as a set?

G

Any Haltech experts out there to answer this?

Which heltech is it? I've never seen an interceptor, but seen lots of piggyback set-ups. Depending on the model you may be able to get it to run perfectly as a standalone rather than a piggy back (assuming tht's the current set-up).

It'd save you shelling out for a new ECU - then again, selling the haltech and buying an MS and getting G to help you might work out to be a cheaper long term tuning solution. I'm sure someone was selling a near new MS cheap on this forum too.?

[davekmoore]

Piston small.jpg

Two surprises:

1. It's the front rod that gave up.

2. No damage to the head. Even the tang on the plug is untouched.

All the plugs and the head look as if it's been running rich generally if anything so maybe the failure was just mechanical. The only thing I'll know for sure is that there was a combo of some or all of too much power/boost, not enough cooling, the turbo maxing out so producing even more heat, the injectors being too small, a hot day and the ECU(s) not being capable of pulling advance or boost.

No surprise that there are holes in the block and in the sump. There goes $700 on a core charge. Wonder if The Boss would like an interesting coffee table?

[davekmoore]

I'm sure someone was selling a near new MS cheap on this forum too?

I may have failed to notice that, and I have now been convinced that MS is the way to go. Point me at the cheap one please.