kpr's starlet

[kpr]

Should hopefully make it this year! 

[shrike]

Keen to see this vs @Romanand the echo

Also @kpr not sure if you have considered it and I hope the T50 keeps going well but have you thought about going to a J160 with one of SQ Engineering's kits not sure if they are heavier then the T50 or better with higher revs but might be an option with more available spares long term

[Metalhead96]

1 hour ago, shrike said:

Keen to see this vs @Romanand the echo

@kpr

Hot version style 90s touge battle? 

[kpr]

 

Yes i need to redeem  myself and all 4age's for that matter, after @Roman beat my NA pb  .01 seconds or something silly

blue jelly bean time: 13.49 @ 99.5mph and 2.09 60ft.
Its great grand fathers time:

wow 2018, didn't realize it was that long ago.    Should have another 15kw or so than what was running on that pass.

 

As for the gearbox,  It seems to be working good now, with the new parts and angle grinder machine work.   but yeah would probably go j160  for the next move if had to.    rather stick with the t50 though.  lighter and dont have to mess around with new clutch combo, driveshaft  and making it fit in the tunnel.   
Engine  uses rpm to make the power, so doesn't make gearbox breaking torque.  but im still hesitant to put a lot of grip into it, to get it down the 1/4 mile quicker.

 

 

 

 

[Roman]

I would happily lend you drag tyres to put on the back of this to see what it could do. It will be an absolute weapon! 

Drag tyres reduce shock loads, good for gearbox, you cant afford not to! 

[kpr]

keen,  if can make it work fitment wise

[Roman]

How cool to see a legit Atlantic motor! 
 

[Vintage Grumble]

So friggin sweet. So when can I order my formula kpr-antics 250hp 4age?

[mjrstar]

Open wheel thing is all sorts of cool...

I have been talking to people that run individual throttle bodies, and often they talk about how a few percent of throttle change can really help with torque control..

 

I find with my Honda (stock single throttle body on an 1800)that realistically between say 60% and wide open throttle there is a bit of a change in noise maybe but not a whole lot of torque or power change..

This led me to think of a few questions does having itb's actually give greater  torque control, does part throttle at lower rpm perform better than wide open throttle, and if so with an e-throttle, could you set up a table to chase throttle percentage as rpm rises.

To this point it'd be interesting to see what a Dyno run at 95% or 70% compares to a standard full throttle run..

presumably under a certain power output there shouldn't be much loss if any?

 

Perhaps @Roman could draw us a graph..

[kpr]

I often do runs around the 70% mark when tuning itb stuff.   if i recall correct, once have a few rpm on the engine, usually just makes the same power till throttle plate becomes a restriction.    I'll see if i can find some runs on the dyno.

there might be something in it, at low rpm where you should probably just change down a gear.   can be a vast difference in the fueling  between high and low load  at low rpm,  on  an engine with aggressive cams. throttle plate tends to "filter" out the big peaks and dips down there.

 

 

 

[Roman]

When I had a MAP based tune on my beams motor, (sorry for saying the B word in this thread) I found that I had really inconsistent sort of results at some pressure ranges. 

So, because I'm a Dave, I plotted some runs at part throttle angles and then referenced back to what the MAP value was.

Like so:




So at 4000rpm, even 60% throttle as a nearly identical airflow to full throttle - Because MAP only changes once the engines demand exceeds what the throttle can supply. 

I was very surprised to see that the engine had 75kpa at 20% throttle at low rpm. Got much worse at lower rpm than that. 
This is why MAF is such a great load axis, just tells you exactly how much airflow there is.

On an ITB motor with Alpha N, I dont have a direct comparison however you can look at the shape of the fuel map to get an idea of when the airflow starts being restricted. 

So at 2500rpm and 8000rpm slices of my fuel map:




So using e-throttle you could retune these shapes to make them linear through the rpm range.
One advantage of limiting the throttle angle to the range that it's only responsive at, at a given rpm. Is that it actually makes throttle more punchy as you're not travelling through a dead zone where changing throttle angle acheives not much. 

Here's another datapoint from the same motor, but with the Toyota Aqua manifold on, so it's breathing through a straw on the intake side through a tiny tiny single throttle:
It flat lines like crazy even with 2500rpm, haha.


My name is Dave, thanks for listening to my story

[kpr]

Edit; ol mate dave quicker on the trigger in the graph game

found some stuff

 

turd engine   100% vs 70%      52mm throttles

a 20v i tuned awhile  100% vs 70%  45mm throttles

good engine from sometime ago.    100% 70% 20% !    

Im just going by the notes i wrote in the run.  plus i dunno how good i was holding the throttle bang on those numbers
couldn't find any closer to 100%  but i recall doing it in the past on 45's or 47's, to see what it would do and was still a small loss at 95%

Also the fuel and timing probably a little different.  but looking like a pretty solid no.  just hold it tapped

one other thing thats interesting   the good engine still makes the same power as the turd at 70% throttle with same throttles. 

 

 

[Roman]

Thats really interesting aye, reach that 4500rpm mark and thats where 70% cant flow enough anymore 

[deankdx]

10 minutes ago, Roman said:

My name is Dave, thanks for listening to my story

My brain hurts, but i think this kind of thing is also a strong feature on carbs especially if too big to give good vacuum signal at big throttle percentage and low revs

[kpr]

yeh pretty interesting how its pretty much bang on the same, then exact point where is a restriction.

[mjrstar]

3 minutes ago, Roman said:

Thats really interesting aye, reach that 4500rpm mark and thats where 70% cant flow enough anymore 

Those graphs are cool, interesting that the deviation is so clear when throttle percentage starts to play a part..

 

One of the guys I spoke to kind of backs this up, he reckons when he swapped to itb’s it became quite noticeable if he didn't get to 100% throttle he didn't get all of the horsepower.. when it was on a single throttle body it didn't seem to matter so much.

 

[Roman]

Haha, that difference in dyno plots is wild! 

Cant wait to see how this goes 

[kws]

Your comment on injector size fascinates me. Bigger injector wastes less fuel because its open a shorter time for the same amount of fuel. Makes sense but wouldn't have thought of it.

[Roman]

Well I think all of the fuel still ends up going in. 
But it's probably more a case of combustion quality, as in, how well it's mixed with the air. 
If you manage to generate a more homogenous air/fuel mix by whatever means.
Then it will report richer on the oxygen sensor because there arent leaner areas in the combustion chamber contributing to the average.

What I found interesting from his testing was that going to 450 deg injector timing was beneficial at higher rpm. I always thought you'd end up reducing that number for higher rpm. 




 

[kpr]

If my drawing is correct. this is pretty close to whats happening in my engine. 

 

 

end of injection being when the ecu closes the injectors.  start is calculated by ecu depending on fuel requirements.     so the more fuel needed, the start moves to left.   also more fuel required i'm moving the window to the right.   so is it loosing fuel out the exhuast on overlap? or some other wizardry?   as can see there is a pretty big opportunity when both the valves are open at 5mm, for air fuel to go which ever way it pleases haha.    I haven't done the math, but would assume start of injection would be well before the overlap.  but then there is also the time it takes to make it from the injector to the exhaust valve before it shuts.

injectors are 980cc running at 40% duty right up top.  approx 100mm back from intake valve