The junkyard approach

T

Tussock

New member
Hi All,

I am looking at using a pair of 4kw 4092, 1520kv, 4-pole brushless DC motors on some TD04 or similar compressors; plentiful 2nd hand!

The Flycolor 'opto' 15OA, 5-12s ESC from Ali' looks good, e-rpm unknown.

The battery will be a 10s pack, 36V (42V max). I have a few e-scooter packs... I may upgrade to leaf battery modules if the experiment succeeds.

Charging system will be a 42V, 5A scooter charger, or 2... Running off a 1600w inverter in a fire box. 😉

This will all be put in my 1998 R34 Skyline GT. It has the RB20-Neo engine (no turbo) which delivers good top end power peaking out at 114kw on paper... but due to the short stroke of the RB20, it's a little flat down low. Hoping the E-turbos will add torque at lower rpm.

From what I've read the RB20 engine management system can handle fuel and air measurement up to 210kw as the GTS-T Skyline having the same system... I've yet to check the airflow meter voltages, but I won't be going anywhere near that; the target output will be up to 150kw.

The parts are all cheap and plentiful as they're common e-bike, RC and 2nd hand car parts. Any thoughts on whether it'll work as planned?.
 
Tussock said:
Any thoughts on whether it'll work as planned?.
Click to expand...
You'll need to draw up real plans using the specifications for the parts. I recall the TD04 turbo being on the small side so what does its compressor map look like, how much air will the motor need at the set goal and where does the air requirement sit on the compressor map, what is the rpm spec for the motor you have selected and will it be sufficient for the compressor wheel speed that will be needed which I'm sure will be high for a small turbo.

I believe it's best to start at the goal end of the plan and work your way backwards to the battery as a means to establish a good hardware start. My preference is for efficiency and long term duration and have found that this combination locks my project into the more expensive end particularly due to the size of the motor, 3.6L and boost pressure goal, 7 psi through the power band to 7k rpm, the most challenging being an ESC in the 16s range at a minimum to generate relatively lower current and heat levels. They're expensive in that range especially given the low price options (Flier for ex) may not be as reliable as specs suggest given some experiences. Higher voltage may benefit here but who knows for sure.

I reached out to rmamba yesterday regarding a 600 amp ESC that has a rating of 22s, 600 amps max at 90 volts and a continuous rating of 600 amps at 70 volts which doesn't make sense given the max amp limit is usually for 10s and the continuous amp rating considerably lower than the max. See the conflict.
 
Thanks for the reply.

That ESC you're looking at is a monster. this one?
www.ebay.com

600A Watercooled Boat ESC 3-22S Flier Controller for Brushless Motor + USB LINK | eBay

600A Boat ESC 22S Flier. 54,000W of max power (600A x 90V). Software and Manual available at Flier Model website. Compatible to DC Brushless Motors. Compatible to Sensorless Brushless Motors. Includes USB Link for windows to set it via PC.
www.ebay.com

I think the peak rating and continuous ratings are limited by heat (like all electric stuff). That ESC appears to have a peak power through-put of 54kw (fry mode, which it could sustain for a minute or 2?) and a continuous power through-put of 42kw.

The 22s pack has a nominal voltage of 81.4V, a fully charged voltage of 92.4V and will be flat at 72.6V

I've found a compressor map for the TD04 but the map doesn't doesn't go low enough to provide info at the 40,000 rpm that the motors will spin at.
1751882521890.png

I will be using 2 compressors and 2 x 4kw motors though... The goal isn't really more power at peak output however... It's to improve throttle response and torque at low- mid rpm, which isn't very good for an RB20(DE) as it has a short stroke. Boost of around 0.4bar dropping down to 0 at 6,500 engine rpm will be satisfactory.

Perhaps the TD-04 is too small... Maybe I'll need something bigger... or 3 x TD-04's!

The Torqamp system uses a single 5kw brushless DC motor & single compressor and dyno's great on a 2 litre engine, but I'm unsure of the compressor sizing...

Thanks for helping the brainstorm.
 
Tussock said:
I think the peak rating and continuous ratings are limited by heat (like all electric stuff). That ESC appears to have a peak power through-put of 54kw (fry mode, which it could sustain for a minute or 2?) and a continuous power through-put of 42kw.
Click to expand...
It's a Flier ESC so the durability and dependability maybe questionable from what I've read, therefore you aim for far more power support than you need with a relatively inexpensive ESC. If you go popular, proven brand name, you can select closer to requirements as they are also much more expensive and likely to perform according to specs. It's a matter of budget constraints, how much are you willing to spend during the developmental stages.
I'm considering the possibility of running two motors off one ESC, it appears if the motors are cogged together and fine tuned rotor wise to be in synch that it'll work very well, however the battery and ESC must meet the combined possible current loads. Two 250 amp max motors will need batteries and an ESC capable of supporting well over 500 amps.

I don't believe a twin project out of the starting gate is a good idea, simple has always been the better part of valor in projects like this as someone who has built a few twin traditional turbo setups. It ends up being a lot of unnecessary extra stuff. I was happiest with a single turbo.
 
I have a background as a service and repair mechanic (15 years) and have built many RC models and racing drones... 2 motors is easy... Even 6 motors on a hexacopter drone is easy, just a bit more time consuming... I've also rebuilt an e-skateboard (2 motor, 2 esc type) and have plenty of experience with both lithium and brushless tech and ESCs up to 4kw.

Compressor sizing appears to be my biggest issue.... So I'm looking for a compressor that'll consume 4kw at 40-50,000rpm... Any one got maths for that?

I'd also like to run a bypass, for when the E-turbos is switched off... Like this chap:


Where'd he get his check valve, what type of check valve is suitable for good airflow?
 
Tussock said:
I have a background as a service and repair mechanic (15 years) and have built many RC models and racing drones... 2 motors is easy... Even 6 motors on a hexacopter drone is easy, just a bit more time consuming... I've also rebuilt an e-skateboard (2 motor, 2 esc type) and have plenty of experience with both lithium and brushless tech and ESCs up to 4kw.

Compressor sizing appears to be my biggest issue.... So I'm looking for a compressor that'll consume 4kw at 40-50,000rpm... Any one got maths for that?

I'd also like to run a bypass, for when the E-turbos is switched off... Like this chap:


Where'd he get his check valve, what type of check valve is suitable for good airflow?
Click to expand...
The initial math for determining the foundational equipment is straightforward given it involves basic engine performance parameters, the most important in my opinion being naturally aspirated peak flow air needs and expected flow requirement at desired power and rpm level. That is the value plotted on the compressor map which will identify the necessary compressor speeds to reach it. If you're intent is to use two TD04 units then perhaps they're suitable after all unless they're combined use ends up being too much for your requirements as your airflow needs must be divided in half and that value plotted on the compressor map to make sure airflow requirement is on the map and not in the surge or choke area.

The Borg Warner matchbot calc is extremely helpful in quantifying this. Enter your boost level, and look for the "Shaft hp" value in the data near the hp and tq values. There's about 745 watts per hp which you can use to calculate your motor requirements relative to the compressor speed requirement for the type of over drive gearing you will likely need using such small compressors. The map you listed has a 90k rpm speed at the first step on the map for ~5 psi, given your bottom end performance focus, two turbos will probably be too much. This is why the P-2 is so popular, it has a low rpm requirement and broad range of useable boosted airflow from way down low in the compressor rpm range.

BorgWarner MatchBot

www.borgwarner.com www.borgwarner.com
 
... And the junkyard gods have provided! I have acquired, for FREEE! A TD06H-25G Kinugawa anti-surge turbo!

1752737827293.png

Better still, the compressor map goes down to 46,100 RPM which is achievable with a 4092, 1520kv motor... Provided 4kw is enough to drive the compressor to that speed... The borg-warner calculator looks good for a rough guesstimate at shaft power being<4kw at 5psi @ 2000rpm dropping to 0psi @ 6000... If demand exceeds 4kw then it could get a bit hot... I guess I'll find out!
 
It struck me watching that video that are lot of guys are missing another huge benefit in running the P2 SC. It barely restricts any flow to the engine at airflows below approx. 190g/s (25lbs/min). I have proven this on my engine, a13B rotary which consumes approx. same amount of air as a 3.3L piston engine. I know this because I have done back to back testing and power only started to drop at that flow rate (pretty close to redline on a 13B). So, there is no need to run that check valve for N/A use if you use a P2 on any engine below about 3.0L.
 
Love rotaries! I've owned an FC3S RX-7 and RX-8 type S, the redline on the 13B-MSP was 9,500rpm. Great cars!
The P2 sounds ideal for my RB20, but as I'm using scavenged parts... beggars cant be choosers! :ROFLMAO:😂
The TD06h compressor is a good size but I think it'll restrict the intake a bit. I guess I'll find out. 🤔
It'd be good not to have to #@(< about with a check valve. Best part = No part.
 
Airflow meter test is now done and it looks good, as peak output voltage was 3.6V at 6500rpm, wide open throttle

I think max signal voltage before the ECU will log a fault will be somewhere above 4.5V so there's plenty of room for boost on the stock engine management system.

Rumour has it that the ECU on the RB20(DE) is the same as the RB20(DET) and good for 210kw... 🤔
 
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