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Ned's 7K Drop Hatch Starlet


Ned

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Whaddaya talkin' 'bout Jonesy? Cam obviously wants to put slide throttles on the landy, who could blame him with such a magnificent beast!

 

Oh lol, Na OMS, I am all about solder, I even made a post mocking the antisolder brigade in my Alfa thread when I replaced the motor/ converted from genny to alternator.

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  • 3 weeks later...

"Some bad news though, wont be running it on my own hardware for the next little while, because the code (FreeEMS) isnt good enough to handle the factory trigger setup, so i'll have to write my own code to do that and there isnt enough time for that before burger boes"

 

Just to clarify about this statement, it's not that the code isn't good enough, it's that the code doesn't exist. In FreeEMS the things that read engine position are broken out into entirely separate things called "decoders". There is a decoder for 36-1/60-2/etc, another for 24+1/12+1/etc, another for evos/mx5s, another for RB20/25/26/30, etc. No one has ever wanted to run an engine from a signal this devoid of useful information. The actual code required would be in the order of 50 lines and half an hour (mostly copy/paste). It would suck, though, just as it is sucking on MegaSquirt and sucked on the factory ECU. Hence my advice to attach a missing tooth wheel to a pulley and get some good data to do good things with.

 

Anyway, new code or new trigger wheel, I'm looking forward to helping Ned get his hardware working and start rocking FreeEMS in the new year :-) Should be good fun.

 

 

What will you have in the way of datalogging/feedback when your own ECU is going?
 
Same as if it were a megasquirt? 

 

 

Different. In some ways FreeEMS datalogging is a lot better, and in other ways it's worse. Similar, though, random log image from my viewing app here:

 

RobsR33RPMTraceShowingBreakupJustPast4kR

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  • 4 months later...
  • 4 months later...

so.... i want more power.

Last time i had a 7K on the dyno, she didnt make any power over 5000rpm, and peaked at 4400 or something. (a mighty 45kw). Up until the 4400, the curve looked good, and i kinda want to extend that curve a bit by 1000rpm or so and make some more power up there.

1) How do i go about figuring out what to get? i'm guessing i can't just call the cam guy and say "give me the thing i want!" and get the right thing.

2) Am i going to run into issues with the valve springs? Also pretty sure its hydraulic lifters, that going to be a problem?

This is my first internal engine modification, so i basically know nothing. I've heard plenty of things, and can make myself sound knowledgeable and can speculate like the best of them, but kinda want some expert advice before i jump down the rabbit hole

This is the "perfect outcome" in my head (excuse the high accuracy graphs)

black is current, green is what i want

Possible? or am i dreaming?

bITpwK.jpg

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Hey so for starters what are some of the basics about the engine? 
 
-Displacement
-Bore and stroke
-Compression ratio
-Valve lift / duration (if known)
-RPM at which the engine makes peak torque and peak horsepower. 
 
When you know these things as a baseline, you can look at another similar displacement engine that acheives what you are wanting, and examine the differences. 
 
Like you might find that best place to start is a higher compression ratio, or more cam duration, or a bigger throttle body, or whatever. 

Or you might find that aftermarket common parts that will fit could help (like a hot cam from a 4k or whatever)

If you have any datalogging capacity with your current ECU, then this will tell you some information about where the engine is currently at. By looking at MAP sensor pressure drop and a few other things.

If you want to go down the ITB route I will donate a set of silvertop 4AGE throttle bodies to the project. 8)
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Cheers roman!

I wanna stay with the current single throttle, but thanks for the offer :D

It's an 1800 cc 4cyl

Bore of 80.5 mm and stroke of 87.5 mm (essentially making it a stroked 5K with a slightly wider and taller block)

I have no idea about compression ratio sorry, or valve lift but i'll see what i can find.

Peak torque was around the mid to high 2000's i believe? about 2600 or 2800 from memory? was a pretty nice flat curve though if i recall and peak HP at 4400

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I would say the stock 7K cam timing is conservative and aimed towards low-mid range torque delivery (ideal for the LiteAce etc vans they came in). 

 

I guess you need to look at rod to stroke ratio too in order to examine if the 7K is capable of revving much higher without vibrating itself to bits. 80.5 x 87 bore and stroke isn't terribly undersquare but if Toyota achieved that extra stroke by shortening the rods drastically you may find excess harmomic vibration and extreme piston acceleration speeds at higher rpms.

 

For instance a Mitsubishi 4G62 1795cc engine has a similar 80.6 x 88mm bore and stroke but has the same 150mm rod length as the 4G63 which happily revs beyond 7000rpm.

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I can currently happily take it to 5500. Rev limit set to just shy of 6000 it think and seems happy to be there as well, just no point as it makes so little power there.

And yes, they do us the same rods as a 7A.

Just in case it wasnt clear, i'm not looking to build an 8000rpm screamer, but it would be nice to make power until 5500, maybe even 6000

Basically, i just want a cheap simple way of adding a little power for not too much money before summer/Drag Day in a couple months

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Have a look at the duration/lift/base diameter of 2K/3K/4K/5K cams and see if any are more agressive than the 7K cam and try swapping one in.

 

*edit* looks like it's only the 5K that runs hydraulic lifters so you might be confined to just a 5K cam if you can find one. Though apparently you can swap in Holden red solid lifters and Datsun A12 push rods to eliminate them.

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