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Twin charged mischief –a risky parochial build, predicated on twisted logic

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Twin charged mischief –a risky parochial build, predicated on twisted logic

Old 02-11-2018, 11:34 PM
  #81  
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Originally Posted by Leafy View Post
0.4 seconds?! is that right? Thats worse than my turbo.
lol, at what, 5000 rpm?
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Old 02-12-2018, 10:26 AM
  #82  
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Any data showing time to boost for the 6258/6758 would be interesting to see -please post! I did see a couple of posts for the 2560, which were about 1 second, but I don't recall the RPM.
Yes .4S is real. It feels much faster than that, seat of the pants wise. I would very much like to reduce the volume of my intercooler, but even with no intercooler at all, I am probably looking at a minimum of .2 seconds.

AND then there is the time for the turbo to spool. When I was running the turbo by its self, it would take a tad less than 2 seconds for the turbo to to spool fron 40KPA to 23psi at 5000 rpm (much faster to 6psi)!. I guess this is what you get when you combine an old large turbo with a cheap cast manifold.
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Old 04-23-2018, 11:30 PM
  #83  
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The weather has finally gotten nice, so this last weekend I had the car on the road to iron out the bugs.
Had some initial problems with a bad check valve, and the SC pulley hitting the new front sway bar, but outside of that everything is good.

Boost levels are up a bit, for 2 reasons.
1. the SC is newer, and tighter so am seeing just over 2psi more, below 3000rpm. (less above that)
2. I leaned out the mixture (from ~ 11.0 to 11.4) over the 4000-7000 rpm range, so the turbo spools quicker, unloading the SC about 400rpm earlier and
getting up to 25psi sooner. When the SC unloads, boost is now at about 23.5psi, compared to 22psi previously.

I doubt either of these items will make any significant HP difference, and I am sure the SC output will drop to the level of the old one after it wears in.

Made some other electronics changes, to hopefully improve some minor issues.
1. When I had just the turbo, and I would flat shift, the boost would drop nearly 10psi, and would take about 1/2sec to recover. This is with a 7800rpm redline.
I have added a high side switch, so when I put in the clutch, the bypass (ETB2) will close, forcing the supercharger re-spool the turbo. (Oh, and I need to shift quicker)

This should reduce the drop, and the resulting spool time, but it remains to see how effective this will be.

2. I added circuitry to the MS1(electronic throttle body controller), such that when the bypass (ETB2) opens, the throttle feeding the supercharger will close slightly (this is programmable and currently set to about ½ throttle).
This restricts the amount of air going into the supercharger, so it does not build up boost in the outlet piping. (I tested this last year)
Not entirely sure if this will improve efficiency, but I am hoping it will. I will need to measure the output temperature of the supercharger while doing this to confirm this isn't
overheating the supercharger. During these conditions, the supercharger is a parasitic load and not doing any useful work. It is pushing against a 4.6psi wall at 7000 rpm
which means I could save some HP if I can negate this pressure. If restricting the input causes something bad, I can add another valve to dump to atmosphere.

3. Last thing I have done is add a switch to the dash to allow for a secondary throttle map.
I normally tune the throttle, so the pressure between the supercharger and manual throttle body is 95kpa (ambient pressure). I
can tune that to easily be much more (I changed all the settings over the winter, and when I first got the car running I was running 9psi between the supercharger and manual throttle body.
This gives you great throttle response, but makes a racket)

Here is what the tuning window looks like, which I use for tuning the electronic throttle body.
I have taken the output from the TPS on the regular throttle body, and fed it into the map input on the MS1.
The TPS I have, outputs from 34KPA (0% throttle position) to 185KPA (100%) –Gauge #5 and #2.

Gauges #3, #7 capture the calculated throttle position the system is trying to attain, while Gauge #8 reflects actual position.
I am trying to get Gauge #7 to stay around 95KPA. (Gauge #6 is supposed to reflect the fuel VE setting but isn’t currently working.)


So I tune the throttle body, by adjusting the fuel ve table. This way I can tune the electronic throttle position, by RPM and manual throttle position.
Still have to tune the throttle body, get the swaybar clearing the front pulley and then get an alignment.
First event is over 3 weeks away, so I have plenty of time.
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Old 08-06-2018, 03:58 PM
  #84  
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It's been a while since my last confession.

It has been a good summer. Got in quite a few autocrosses and 2 track days so far and surprisingly, no big problems.
Small ones, like the exhaust falling off, some overheating and the occasional clamp breaking, but so far things are good.

Changes to electronics are working well.
Now, above 5000rpm, the supercharger throttle closes to about 1/2, which reduces parasitic boost in the piping.
During shifting, the boost now drops about 5psi vs previously 10, since the supercharger bypass is closed during this condition.
I thought I wanted a more aggressive throttle map, but after a bit of testing, I discovered that I really needed something that was much more progressive.
The throttle was more like an on off switch, which made driving competitively in an autocross, impossible.


Did get the xidas and brake prop valve in there. Here is the current under hood.

I upgraded the clone Rad fan with a SPAL, mostly due to some events with a small turnout and the need to run 4-5 runs in a row.
Plus it's been a pretty hot summer here.


An underhood bling item.


And I recently picked up a pair of drag slicks 23x8 which I mounted on some 13" wheels.

I repurposed a t-bolt clamp, to make a driveshaft loop.
The loop is bolted to the PPF.




Seats and big brakes are on the list for probably the fall, when things slow down a bit. I'm tired of dealing with badly faded brakes.
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Old 08-06-2018, 09:34 PM
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That counts as a driveshaft loop at your drag strip? That band clamp couldnt keep the driveshaft from a lawn mower from whipping.
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Old 08-06-2018, 09:50 PM
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Yeah - that loop probably wont do a damn thing
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Old 08-08-2018, 10:46 PM
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^ Good catch, you're right. I thought I could use something I had, but didn't think it through. I do think it would work just fine on a lawn mower though
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Old 08-09-2018, 02:31 AM
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Can we get some videos or a dyno plot or something? Looks like a wicked crazy contraption and I'm dying to see it in action or a plot showing us if "it was all worth it"
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Old 08-09-2018, 06:19 PM
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Originally Posted by 18psi View Post
Can we get some videos or a dyno plot or something? Looks like a wicked crazy contraption and I'm dying to see it in action or a plot showing us if "it was all worth it"
I did post an autocross video and a Virtual dyno graph earlier in this thread. (Post 62,74) Those give a rough idea of what the system does.
When you’re in the car and you floor it in 5th at 2000rpm the car feels pretty quick, but when you video it, the car is just slowly accelerating.
Pretty boring and not worth posting.
Also, the 2 dyno companies I used to deal with, are out of business, and I have not found anyone who is interested in setting up their dyno
unless they can charge me a couple of hours of tuning. So, I won’t likely be posting a dyno either.

When I run the drags, I will know if the top line numbers in virtual dyno are close to real, and will shoot some video
but that will not really tell anyone, if “it was all worth it”.

IMO, 99.99% of people will argue a twin charged system is not worth it, because you can go EFR with an off the shelf system,
and get pretty close to the same performance. I would agree with this statement.

Of course, building something like this, or the projects that Leafy/Pat/Ted plus many others have done has more to do with a vision
or passion for something different. Performance is part of the goal, but many other things add up to making the project “worth it”, for the builder.

Personally, I like reading about these and other projects, because they are interesting/entertaining, and they drive me to get off my ***
and get working on the car. Sometimes I need the motivation.

I am not saying that this project was not worth it for me. I came pretty close to my performance goals, and find the result to work very well on the street
and in the small lot autocross events I usually run the car in. Unexpectedly, the car also generates a huge amount of interest.

Now, I am keenly interested in a turbo/compressed air setup. I think that would be very cool project and present some interesting challenges….
Of course, I really need to stop thinking about this and just drive the damn car.
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Old 08-09-2018, 09:22 PM
  #90  
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Amen brother
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