No problem with the power output , but it's a 7670 at only 12.5psi ! Does this seem odd to anyone else ? Anyone have any thoughts on how this could be achieved ?

 

E85 and a half bridge, so doesnt sound impossible- there just woulnt be much room to turn the boost up and make more power since the compressor is already getting close to max flow.

 

I can see low psi with a bridge on a bigger turbo with low back presssure ..... but with the 7670 EMAP would be way over IMAP .... does a BP normally respond like this with a small turbo and high EMAP?

 

Hard to say what emap might be without measuring- I wouldnt expect it to be very high only having to push 12-13psi.
Its not that 7670 is such a small turbo, just that people who go with bridge porting typically go big on turbo sizing.

For decades T04B, T04E, T04S with the same 57/76mm compressor were standard turbos for the rotary. Back then many people opted for smaller .85AR T4 exhaust housings (*gasp* can you imagine).

 

I put that scenario on Matchbot and got an EMAP of over 20psi, even after allowing for near zero back pressure on IC , intake and exhaust . The Compressor is way off its efficiency island (down around 40-50%) to flow 50 plus lbs of air too. Ve needed to be over 130% in order to flow enough air. to make that power.

 

When you are cross comparing BIG port work you really need to be looking at turbo shaft speed, and not IMAP. The BP is ingesting a lot more airflow( higher VE numbers). This is why you generally see the bigger port engines make more power per psi, however they max out the compressor wheels MUCH faster.

 

^^
Matchbot sounds about like what I would expect.

Can the turbo/engine do what the dyno shows- probably.

Why would that combination of turbo/porting be chosen? No, idea.

 

I do tend to question things that don't make a lot of sense to me so just to explain why I questioned it :
For every other result I've seen for that turbo, to make that kind of power took 18-20psi IMAP or more.
That's a lot more boost than the next size up turbo takes which makes sense when you look at the compressor chart.
My understanding was that to make overlap work well you need EMAP to be on a par or lower than IMAP .... I don't think we have anything close to that here.
To put in a half bridge and get an 8 psi drop in IMAP for the same power .................. I'm struggling to understand.
Unless there is some other majic going on ...or a mistake.

 

The customer actually just swapped to our EWG 8474 turbo system, will be a dyno overlay( same dyno/tuner/shop etc etc) in a few months...We've already delivered the kit, just a back log on getting it installed...

 

Now that would be a very interesting test ... overlay at the same boost !

 

Do the miniature American horses go some way to explaining it? I will have to dig out my old spreadsheet, I had worked out specific output factors that matched pretty much any quality engine package with varous porting/peak power engine speed.

 

Not questioning what the engine can do ..... more why that particular turbo (in combination with the engine porting) shouldn't be able to do what's stated.

 

was just sitting back and watching in lurk mode to see how this developed on it’s own

now that it seems to have stalled perhaps the thing to question is whatever information or thought process is leading you to think it shouldn’t be able to do what it does, when in fact; it does.

.

 

I think people get confused on what works and what is more optimal in one respect or another (emp or whatever).

Like, show me a stock turbo car that runs 1:1 map to Emap.

Driveability is more of a priority for most oems.

 

There are but specific power is pretty low then. We recently made a 2.0 tgdi engine for a eastern oem and it has not a single point in charged area in the map that has lower boost then backpressure. The key is turbo matching and selecting vvt position where you stay in the center of the compressor map on the peak efficiency. For example
this engine makes only 110 kW from 2.0l displacement, which is virtually nothing. At rated power the VE of engine is below 55% because of the very miller like intake cam (early closing). Gage boost is a hint over 30 psi. This all might sound weakish, but the specific fuel consumption is very good. Center of the map has a big island below 220g/kWh and at rated power is below 235g. (43MJ/kg equiv)

 

You mean late intake valve closing surely?

 

no, early. you close intake way before bdc of intake stroke so you reduce the filling quite alot. the charge cools down during the further expansion going from IVC to intake BDC. this also reduces the effective compression ratio. The advange is a cooler charge and a lower effective CR so a big advantage on spark efficiency due to the decreased knock. On the expansion stroke you have the advantage of the high geometrical compression ratio ~11:1, which increases thermal effciency.

 

Boost is the most misreported measurement in the dyno process. It's rare that you ever see the boost curve so it's often just conveyed by word of mouth. There is a classic example in the 'related thread' below this one. On FB that same dyno is quoted at "310whp @ 6.5psi" . Now go and have a look at it and see for yourself . 8.5psi tapering down to 7psi at peak power on a dyno in 'comparison mode' . No lies told ...... just undereporting of reality.
So now do we think that all we need for 310whp is 6.5psi on a "large streetport 7670", or do we go with our own experiences and be realistic?

 

Ok, achieves similar to very late closing with a touch less pumping loss.

 

Here is my result. Got it tuned by Steven Kan at PRT Performance (great guy). Not sure how much his dyno differs in numbers than other dyno's. My 13b is stock port, EFR 7670 IWG, used the wastegate and recirculation valve it came with. 3 inch exhaust from downpipe all the way back to muffler. Unfortunately we had to put the factory ignition setup back in as my Ign1A smart coils was breaking up around 6500 rpms. I will have to sort through it and try to get it working. once I do I will send car back to him to retune. He took this tune up to 1 bar of boost. I have 550cc primary and 1700cc secondary injectors. I am running the Apexi Power FC, using the apexi boost control kit which comes with the apexi map sensor and solenoid. Tuned using the Datalogit program.

 

How does the car feel? 300 RWHP isn't a slouch I imagine with the response you're getting from the EFR 7670. Wondering if @Turblown sees anything on this dyno graph worth pointing out. Wondering why there is that dip in HP and TQ around 3700 rpm etc..

 

Man it feels great for what it is. I cant wait to take it out on the road course. Yeah that dip could possibly be from my setup. I Welded and fabricated all the parts on my car. Could be manifold design perhaps, but yeah be nice to get input on it. Below is what my setup looks like. Id like to put this car on another dyno if i can find a local shop near me with one to compare it.

 

To me the "dip" looks like boost control issue.

Specifically, I used to get that shape dyno when boost spiked a couple psi above set boost just as/before the WG opened and then settled.

I had to drill the bleed port in my Hallman Pro RX a bit bigger to get a perfect boost onset.

Looks like a really nice set-up!

 

thanks, i wonder if upgrading the iwg and recirculation valve to turbosmart would correct that maybe. Or if its the apexi boost solenoid as your implying. Thanks for the input, ill look more into it.

 

nice welds!

is that a giant catch can?