Full tune of 68HTA, KSTech 73 MAF, Racer X FMIC and DW750s

[Ruby Red Rocket]

Little Blue--and those considering the HTA68 and/or who have owned something like the full sized 18g discussed in the following thread (POST #41), I am something like confused. So, help, please, if you can.

 

http://forums.nasioc.com/forums/show...o+for+the+2.5l

 

I have been following with great interest, looking to chart my own upgrade path. The 68 sure looks good on paper, in graphs. While it isn't some kind of miracle, it sure looks like a very good piece. Very good power bottom to top. And then I read post #41 (in the forum above) and all that ranting about the 2.5 motor needing an 8cm housing lest it be "choked" off. Yet there are the numerous reports of how fast the 68 is compared to a 20g, even. I don't know what to think. It leads me to these questions:

* Is there an aspect of turbo performance that is not, perhaps cannot be captured by a graph?

* Just how much can one glean from a valid graph?

* Would an 18g be more satisfying to drive at low RPMs or off throttle (like in a corner) because of the 8cm turbine housing?

* How would the 68's performance be effected if it were fitted with an 8cm exhaust housing or if the 7cm housing were PnPed?

* Is the author of post #41 just, how you say, stuck in the mud? An "old dog" who refuses a new trick? How can he be right about the 68 (that it's too small for the 2.5 motor), if Little Blue and others are right about the 68 (it runs like a champ)?

 

From my own little "wanting to figure out the LGT universe" department...RRR:spin:

[NSFW]

http://forums.nasioc.com/forums/showthread.php?t=1904978

 

Same link, without the randomly highlighted words.

 

FWIW, I have seen a bunch of people post their opinions on how the TD05/TD06 7cm/8cm housing options affect performance, and I have come to the conclusion that nobody really knows what they're talking about. Or, the one person who does understand it is lost in the noise, which amounts to the same thing: take everything you read about those exhaust housings with a large gain of salt.

[LittleBlueGT]

I posted my findings and opinions on a different NASIOC thread:

 

Logic of HTA68

 

I could be wrong, but this is my take:

 

7cm vs 8cm. It is not the actual size that matters so much. Physically a 7 cm housing is still large enough to support well over 400 whp (don't forget, half of the flow will go through the WG). We just relate those sizes to things we know. ie: 7cm in the turbos we know chokes off on the high-end.

 

But, just what happens when we have a more efficient comp wheel (hta) it doesn't need as much power from the turbine to flow as much air, there-fore more air will flow through the WG, kinda negating the neg side-effect normally associated with a 7 cm housing!

 

Changing the efficiency of certain parts of a turbo changes all the rules of thumb we used before.

 

I wish I could see a comp chart of the 47 lb wheel the hta68 uses.

 

 

An efficient wheel requires less exhaust gas through the turbine to flow x amount of air.

 

As an example: (just assuming numbers here)

 

20g requires 22 lbs/min of flow through turbine housing to flow 44 lbs/min from comp wheel

 

hta68 requires 20 lbs/min of flow through turbine to flow 47 lbs/min through comp wheel

 

I have no confidence in those exact figures, but if the idea is true, then you get my point. A more efficient wheel helps out a less efficient housing.

 

There are turbine flow charts for a reason. Read what I said. It is not a bigger wheel that helps, it is a more efficient wheel (and I don't mean bigger = more efficient), I mean a wheel that requires LESS energy (less input energy from turbine) to flow X amount of air. I believe that any hta comp wheel is just that.

 

More air going into an engine means more air coming out, of course. But a wheel that requires less energy to spin up to the speed required to flow X amount of air means the WG is open wider (or more if EWG) and that helps drastically in the case of the 7 cm turbine housing.

 

 

There is more on the thread.

 

FWIW Geoff from FR agrees with me, even though he has nothing to do with the HTA68.

[Ridgeracer]

Good luck talking to those guys on NASIOC...

[Infamous1]

Good luck talking to those guys on NASIOC...

I was reading that thread for literally two minutes and just gave up....

[LittleBlueGT]

I was reading that thread for literally two minutes and just gave up....

 

I would like to try and 8cm housing. Anybody know where I can get one?

[Infamous1]

I would like to try and 8cm housing. Anybody know where I can get one?

That idea did seem attractive to me, most specialty turbo shops should carry them.

[LittleBlueGT]

That idea did seem attractive to me, most specialty turbo shops should carry them.

 

My EWG is hard plumbed back into the DP.

 

http://i248.photobucket.com/albums/gg194/littlebluegt/IMG_5756.jpg

 

As long as it doesn't change the dimensions on anything, it can't take too long to try it out.

 

If it worked well in the 8 cm housing, I wonder why they wouldn't offer it in one?

[Ridgeracer]

It seems logical to offer it with the 8cm if it worked well. One could speculate a 20gHTA with an 8cm hotside down the road.

 

How much would the 8cm hotside cost vs a 7cm..? I'm think not much of a price difference considering the overall price of turbos anyways...

[wsmith30132]

^^^^

 

haha, I was going to post you the link to a thread on Nasioc I read the other day where someone just put the 8cm housing on their 68 but saw you had already posted on there. Took me 10 minutes to find it again

[NSFW]

If it worked well in the 8 cm housing, I wonder why they wouldn't offer it in one?

 

After all the 68HTA excitement dies down, they'll offer it with the 8cm housing, and they'll be the turbo of the month again. Ka-ching!

 

More seriously, someone said in that other thread that the 7cm housings cost less and are more readily available. That might be the only reason FP prefers them, it wouldn't surprise me if they made the decision based on cost and a steady supply.

[Ruby Red Rocket]

...take everything you read about those exhaust housings with a large gain of salt.

*****

 

Harra Brush and LBGT-- thank you for your excellent explanations. I suspected that compressor efficiency had to be at the heart of the HTA's superiority (facts, such as physics, are stubborn things). Now, why otherwise smart and turbo savvy Subie mechanics would hammer away at the same old (and not quite right) cliched explanations when the facts point in a different direction....

 

Said Mark Twain: "I wonder if God created man because he was disappointed in the monkey?"

 

Thanks again gentlemen...RRR

[NSFW]

Geez, I need a new avatar.

[enthusiast]

Geez, I need a new avatar.

 

:lol:

[LittleBlueGT]

Can a mod change the title to :

 

Full tune of 68HTA, KSTech 73 MAF, FMIC and DW750s

 

 

On a different note, I was reading up on the new 430 Ferrari replacement, the Italia. Pretty sweet car! I noticed that the exhaust was looked at and tweaked to get back pressure from 7.5 to 5 psi.

 

Why do I care? Well, about 2 years ago I did a back-pressure test on my exhaust. I ran a gauge from the WB bung in the DP. I saw about 5 psi back pressure from 4500 rpm on.

 

I have a HFC, but probably not quite the same as full emissions ready car, I assume the Ferrari has at least two cats (sets of cats) in series.

 

But now I have a reference point for back-pressure. I would say my exhaust flows well!

[Ridgeracer]

How did you set that test up.?

 

BTW...I need to change my thread title as well too. Car is running and tuning just fine. Still in the process of incrementing WGDC to hit targets.

[LittleBlueGT]

How did you set that test up?

 

I ran a gauge from the WB bung in the DP

 

Got he correct male thread fitting to a barbed hose adapter, bought an inexpensive gauge (0-16 psi or something like that) and ran the hose through the window.

 

I lasted about 40 mins til the heat wrecked the gauge.

[NSFW]

Someone on another site said that you can do that long-term if you use a long thin metal hard line (thin = 1-2 millimeters) to dissipate the heat. It's kinda tempting.

[LittleBlueGT]

Someone on another site said that you can do that long-term if you use a long thin metal hard line (thin = 1-2 millimeters) to dissipate the heat. It's kinda tempting.

 

But why? In case your cat goes?

 

To me it doesn't seem like a worthwhile thing to monitor. A 4 channel EGT would be much more useful IMO.

[Ridgeracer]

A 4 channel WBO2 sensor setup for each cylinder would be another wish list item too...

[NSFW]

But why? In case your cat goes?

 

To me it doesn't seem like a worthwhile thing to monitor. A 4 channel EGT would be much more useful IMO.

 

Just curiousity, really. I'm pretty sure I'm going to have 4-channel EGT by the end of summer. I doubt I'll have an EGBP gauge though.

[Infamous1]

Can a mod change the title to :

 

Full tune of 68HTA, KSTech 73 MAF, FMIC and DW750s

 

 

Done

[Ridgeracer]

Done

 

Hummmmm. Could I get some luv on my post since I fixed the vacuum leak already.

[KSTech]

I like the new thread title much better.

 

<<== "Vendor II" status now BTW.

[LittleBlueGT]

Have I mentioned that I hate our gas lately?

 

Just took a LV of a maturely driven 09 WRX completely stock, pulling a few degrees of timing in anything above 4400 rpm and 2.0 load. Worse above 5600 rpm. And this is on Shell 91 octane, which appears to be the best gas we have.

 

 

Makes me want to cry.

 

I haven't' logged my car in a while for two reasons:

 

1) I hate running real low timing on pump gas, and

2) I was still getting a bit of knock on runs in any gear higher then 2nd

 

I figured it was best to wait for new FMIC (which should be on it sway tomorrow). Then I will continue to tune.

 

On a side note, my alky system:

 

Many alky users have noticed a diminishing amount of alky injected as it gets real cold. I was seeing 2 bars of flow vs 7 when it was -15F outside.

 

I have been working on this issue for some time, but never was able to test everything needed. We have the problem worked out now;

 

-I thought it may have been the flow sensor not working properly in the cold, but now that I have the front O2 in the DP, I was able to easily verify AFRs in any temp (before I could only check with my non-permanently installed WBO2, and I didn't like installing it through the window in the cold), I was able to ascertain that the alky system was flowing less, as the flow sensor read.

 

-I then thought it may be the pump that was affected by cold temps, but Richard from Aquamist sent me a gauge, and sure enough it held rock steady at 170 psi, no matter what temp.

 

-this led to the only logical possible answer; when it gets below about 30F the pressure drop from 170 to about 20 psi was enough to cause momentary freezing at the injection nozzle. I then tried mixing in a bit more meth (app. mixture was 70-80% meth vs 50/50 by volume) This seemed to solve the problem. When it got below about -10F or so flow was still reduced a very small amount, but I think it will be easily livable.

 

I don't know the possible long term consequences on my WWF system of running a high meth mix, I guess I will find out. FWIW Richard says he will design an in-line heater to solve this problem for next winter.

 

Now I can run my alky all year!!!!!!

 

 

Cliff notes:

 

-if you run your alky system below 30F, consider running a higher concentration of meth, say 70% or so, if running it below 0F consider running 80% or so