Bogging down at point of turbo engagement. Why?

Thank you k-moe for helping me with this. I have some 3/4 and 1" ball valves I may couple to filters to restrict airflow and test. I'll share results when I do this.

 

You could save a bit of time (maybe) and use masking tape and cereal boxes to restrict airflow at the filters.

Keep in mind that I could be flat-ass wrong, but the easy things really should come first when diagnosing a problem.

 

I run a mostly stock turbo seca with a stock airbox and foam filter. I know all the grief that gets passed around for normally aspirated XJs, but I don't think that applies to Turbo Seca, since it runs on boost, and you're using the surge tank as well, which should smooth the flow just fine.

I would say that you haven't actually verified boost unless you have a boost gauge on the compressor outlet (I have one installed on my surge tank, which is the same line that connects to the waste gate). If you added a manual boost controller you'll need a boost gauge to set preload on the boost controller check valve.

Even if you have boost, you aren't guaranteed to have ignition at the right time. The wiring diagram shows splices from the boost sensor that feeds both the dash gauge and the TCI box. You should at least verify continuity between the B/R and B/Y wires from the boost sensor plug to the TCI and Boost Gauge. The manual also shows a linear voltage curve with pressure. Get some low pressure air (less than 20 psi) and test it. A bike pump can work well for this.

Finally, you need fuel. First is fuel pressure. I also installed an aftermarket fuel pressure sensor to always keep an eye on the health of the fuel pump and pressure regulator. Unfortunately, the cheapest ones are $100+, but that's how you "know." Unlike a boost gauge, you need an electronic sensor, you can't/shouldn't run a pressurized fuel line up to a gauge cluster. After that you need to guarantee that the fuel fills the bowls. If the carbs leak the "bowl" pressure to atmosphere that won't happen on boost.

Finally, having the turbo up by your legs is risky, that thing gets very hot! Furthermore, the exhaust gases are going to lose a lot of energy through all that plumbing (one reason why the turbo is on the bottom amid other design trade-offs). If this continues to be a problem, returning the plumbing to stock, working out the bugs, then modifying might be the best way to sort this out.

 

I may still have an AEM boost gauge out in the shop with all the boost controller stuff. I have a small dial inline NX fuel gauge as well but dunno if it will work.

 

Thanks ManBot, very helpful.
I have 2 boost gauges plumbed from turbo and intake. its difficult to read 1 or 2 psi on a dial gauge whilst full open throttle on a bike I'm still learning to ride, so I can't confirm I'm not getting absolutely no boost. Oh, and I do not use stock boost gauge.
I removed boost controller as part of problem elimination for now.
I WILL check for this continuity, good call.
I WILL check pressure sensor at varying pressures and cross reference voltage to manual spec.
I do not believe it is pump issue. I've tried stock & aftermarket with no impact on issue.
Where did you plumb your fuel pressure in at? Incase I need to do this?
I believe my bowls are full, If I emptied the bowls wouldn't the motor die? or atleast show symptoms of fuel starvation? After i let off throttle bike returns to normal INSTANTLY.
I need to wrap my exhaust... indeed.

Will post update when I perform the two checks.

Thanks again.

 

Just tested Boost Sensor, anyone take one of these apart and "fix" them? output voltage is low.

 

Well that would def cause a major lean condition.

 

Many of them are peizo elements and you can't "fix" them, but I've never seen a MAP sensor from a bike. Pics?

 

For the boost sensor, ebay is your best bet unfortunately. Means you have to take a chance. How did you test the sensor and how accurate are the tools you used to test? That does seem linear, so it's no like it's stuck at 2V. If that's the actual output it will have an impact on timing (the MAP isn't used for fuel delivery only timing advance). Just want to eliminate possible testing error.

For the fuel gauge you can splice in the sensor between the pump and check valve. From the stock setup, there was a 90 degree bend that I could exploit using a 3 way brass tap (home depot) that I screwed two barbed ends for the fuel lines and could screw on the sensor on the back. IIRC I also got some fuel proof loctite for the threads. This was the cheapest electronic gauge I could find: https://www.glowshiftdirect.com/tinted-7-color-30-psi-fuel-pressure-gauge/

 

Wow, so it only retards spark? I would expect there to be some amount of fuel enrichment.

 

I suspect you can wire up a MPX4250AP to match the voltage scale, but it won't be pretty. Might be able to make it fit in the OEM case if it's not potted. Hmm. Are there a bunch of these turbo setups around?

 

It's carbureted. Pressurized carbs in fact, and it just regulates fuel flow like a normal carb but instead of being open to atmosphere, the float bowls are exposed to compressor boost pressure so there's still the same drop in the venturi.

 

12v DC power supply to + -, air regulator with large dial guage 0-30 psi, multimeter + to sensor output, - to DC power supply -

 

I re-conducted the test, pictures provided. 28psi gave me 4.9 V. I took apart the sensor... jeff said something about flexing a strain gauge for adjustment. I'll mess around with that.
psi v
0 2.2
6 2.9
12 3.6
4.9 28

 

Good luck with stressing the element. Looks to me like it's already exceeded stress limits and is failing outside of spec if you read 4.9V at 28psi. You can likely use that MAP module I posted earlier, with a couple of voltage dividing resistors (if needed). The scale looks pretty close to the OE spec. Or, you can grab one off eBay and hope it works.

 

Who ever flexes the element is a magician. I broke the sensor just taking it apart.

Anyone about replacements??

 

eBay has some used ones for around $30. Or you can look into the MPX4250AP. It has 3 active pins, +5VDC VCC, GDN, VOut. If I knew there was demand for it I'd work on a replacement kit.

 

I read the turbo manual it describes how the system works.
the one thing that caught my attention was why Yamaha located the turbo under the bike. 1500 degree exhaust.

 

It has to be wrapped in a blanket or be in a draft to reduce heat soak.

 

Cover it with a chicken.
Tandoori, yumm.