97civixlx

As the the title implies I have a question about the turbos I'm choosing for my J32a2 civic build next year.

There are two turbos, a 8 blade hx35 and a 7 blade hx40.

The goal is 400whp-450whp ran on stock rods.

Now is the hx35 efficient enough to get me to my goal? Or will it, like many other people online have assumed, choke the engine? According to the compressor maps for these two turbos it would appear that the hx40 is better for my application but is it?

Apparently no one has really done this mod, using a twin scroll turbo, and if they have, they haven't shared the results. Only one person has claimed to run a hx35 on a j35. He said that it had instant power but died up top.

If hx35 don't like low boost, and I'm reading the hx40 compessor map, shouldn't it not like low boost either? But if I'm reading it right, the maximum efficiency is at about 15psi is it not? And should put me at 450whp right?

Sorry for the confusing question. Any responses are appreciated!

eHMxhACk

iTrader: (17)

Honda-Tech Forced Induction forum

Click on the link and ask there. It's the appropriate forum for your question.





eH.

Former User

Moved

extremeracer

Use the HX40, but make sure you have a 16cm2 housing ideally. I have used many on 2JZ's which at 3000cc are similar to your J32.
Boost threshold is quite early, and it makes for a fun setup that doesn't fall on its face after 5000rpm. Don't use the HX35, it will lose steam too quickly.

You'd want to run >10 psi to wake the HX40 up, if you run it at 15 psi it will be sweet and at 20 psi or a pressure ratio of >1.4 it starts to really come alive.

97civixlx

Thanks for the reply extreme racer.

The title is a little misleading but your reply was still sufficient . The turbo compressor maps seemed to tell me exactly what you confirmed so that's great! Thanks for your advice!

I got one last question to ask you if you know. Why do people like to state that these turbos love high boost? A lot of people like to say that unless you're running 20 or so psi this turbo isn't worth it?

I mean, the efficiency is still good, but the absolute sweet spot is at about a PR of 2. That's 15psi with like 79% efficiency and 88k rpm for the turbo.

I'm trying to put the least amount of pressure on internals as possible because this is being ran with stock rods. They're not quite as beefy as supra rods, but far better than standard OEM honda rods as these are "forged" acura rods.

Do you know what model car the hx40s came on or would you suggest ordering the turbo online?

Geis

My layman's guess is that it has to do with turbine efficiency. Not sure where the best places to buy em are, but surely you can grab them off eBay of Cummins forums and send them off to be rebuilt if necessary. Even after the rebuild you should have yourself a very nice turbo for under 500

2kdrift

Well efficiency and also the point where its the most responsive..."sweet spot". like on my turbo once it hits 10 psi its very responsive it can go from 10-20psi in less then a second. contrary to popular belief turbos work best at higher boost pressure, each turbo will have a somewhat unique sweet spot where its still in its efficiency zone and very responsive

97civixlx

This is the best compressor map that I could find for the hx40 though I believe it's a little off. I hear these are supposed to Max flow at 60-62lbs a minute. This one shows like 58lbs a minute

But that sweet spot seems to be at 2.02 PR or 15psi.

I mean, I am reading this right? Right?

TheShodan

iTrader: (14)

Assuming a 1psi pressure drop from the intercooler, 2.02PR is about 14psi. But that depends upon the kg/s corrected flow rate of the engine at a specific rpm set. You're not even looking at 1/8th side of the cube here. You're missing A LOT of information.

Volumetric Flow Rate of the engine in (VF) = (rpm x displacement) / 1728*2
Ideal pounds of air
Volumetric efficiency
Max Rpm
Turbine gas flow kg/s (found in the turbine wheel.)

So, say you're at 1500, 3500, 5252, 6800 rpms, you would use all 4 rpm points and calculate the Kg/sec flow rates of each rpm points at about 78% VE.
you'd have .08, .19, .28, and .37 kg/sec respectively. (give or take of course)

For over 400whp at 14psi, you'd be a little laggy at first, (1:1 ratio 4th gear), but by the time you were between about 3500 & 5000 rpms it'd wake up quite well.

Get it to a higher boost pressure level, and you'd do even better (15-22psi).
Just lots and lots of things that even the standard "turbo calculators" don't take into account.

97civixlx

The shodan, please enlighten this young poor soul lol. I've read a lot of forums about a lot of things and I've seen your name around plenty. And I mean A LOT. Lol. I think that's a good thing!

And I've read the "turbo compressor map for dummies" that Justin Sane posted on hondaswap. That's where I'm getting most of this information.

So I have missed a bit of information or jumped to conclusions. I'm just trying to get an understanding of my motor because it's unlike most honda swaps because of displacement and number of cyclinders.

VF = (7000 x 3.2)/1728*2

Now is that 1728^2 with a typo, or 1728*2 as in 1728x2?

Answers are 6.48 or .0075? Respectively of course. Or do I have to do this for individual rpms?

Ideal pounds if air. I'm gonna assume 15-20lbs of air to get me to my goal. Less in my case is more. Stock rods. And it's a good thing if the intercooler robs psi, that means more boost, better efficiency.

I'm assuming the VE is 90% for a 4 valve engine.

Max RPMs will be around 7000 or whatever the j32a2 redline is. Might be more if I decide to cam.

​​Kg/s are listed on the bottom of the compressor map posted. So that'd be close to 65 kg/s?

97civixlx

I used a turbo calculator and plotted the max lbs/min (cfm) at 1,5, 10, 15 psi at 2.02PR.

Im now thinking based on projected line that this is why people say more boost on these holsets are better. It is out of the efficiency range, but its still above 65%

Is this right Shodan?

97civixlx

Whoa, sorry shodan, didn't see that you edited your post.

But yeah, thanks for the information!

I think I'm going to run an intercooler that's a bit bigger for my application so I can run the extra psi. A bigger intercooler should drop the psi 1-2lbs. And a little more boost can be expected to get me into the mid 400s (15-20psi) rather than the early 400s (14 and less psi).

So between the intercooler and potential lower c/r pistons (9.0:1) I should be able to run 20psi on the turbo and feed the engine 17psi accounting for psi loss. Right?

I got a question though, why 78% VE? Is this accounting for the age of the engine? Or is this what v6s deal with for VE?

TheShodan

iTrader: (14)

You're getting there, but you need multiple rpm points at the same boost pressure level to see whether or not you're truly efficient. From your edited illustration, you're only showing one rpm point. That's simply not enough.

Here's an old example of what I mean. On a T4-46 "trim" turbocharger (about 40-43lbs/min) Turbocharger. Notice how the CFM Airflow (which can be converted to lbs/min or kg/s with some easy math) corrected airflow is perpendicular (and thus coincides) with the Pressure Ratio given. Those different Airflow readings coincide with the (approximate) rpm points that the engine sees, given the correct equation values entered.



As for your intercooler;
You don't want too much of a pressure drop in your intercooler. This is a situation in which about 0.5psi to 1psi is about as much as you really want. You start loosing more, that's a boost leak, and basically you're forcing the turbocharger tor run more a higher rotational speed just to get to the boost pressure level you desire. It throws everything off just like any other boost pressure leak. Yes, a larger surface area allows for a slightly larger pressure drop, but after 1psi, that means that either 1) the intercooler is severely inefficient, and is basically not doing its job of cooling the exchange air, or 2) that something is wrong and the cooler is damaged.

What you want is the right type of fin design for the intercooler, and not just going for larger. Larger helps, but not if the space provided for it, isn't allowing it to do it's job. See the discussion on Intercoolers and you'll see what I mean.

Post #61
https://honda-tech.com/forums/forced...3074553/page3/

I used 78% efficiency for the engine based upon a chart I had (from years of collecting) of typical bench flow CFM tests from a variety of cylinder heads. Yes, .90 is used for most 4 cylinders, but over the years I've found that .90 is being extremely generous when it comes to cylinder heads. Honda VTECs (especially the K-series) has almost a true .92 VE, while Subarus are about the same as your J32A2 at about .78-.82 depending upon what's done to the head.
Don't sweat the number so much, the J32A2 you have is VERY efficient, and Tony the Tiger has done quite a few turbochargeed setups with that engine (In the Actual TL Chassis). Besides, two heads are better than one.

97civixlx

So avoid pressure drops in the intercooler. Yes. And if you're correct about the VE, it's done wonders to my set up. Well the hypothetical one on paper now of course lol.

So, I redid the math and the graph and this is how it stands so far.

J32a2 w/ hx40
VE = 80% (the median)
Max engine RPM =7000
Max PSI= 20
This is the graph redone at VE=80% on a 3.2L engine. RPM values are in the associated colors though i really dont know what this means.

That i should be spooling around 3k rpms at full boost? Full boost is going to be set at 20psi.I mean, if anyone including shodan would like to read another turbo compression map, the work has already been done for you lol.

Do you have any suggestions shodan on the size of the intercooler I should run? Not that I haven't checked out the thread, just that there isn't a definitive answer on what's best. V6s Are different from the I4s afterall.

TheShodan

iTrader: (14)

Heat exchange is best exchange regardless of engine size or type. It's mainly based upon the fin design as I stated in the discussion .

Garrett is the core you want. 25 x 10 x 3 is about the size. It will be different size for other style cores


​​​​

extremeracer

Hi, I'm sure The Shodan's informative posts have answered your question. It is somewhat true that the Holset's in general like > 20 psi but that doesn't mean they are not efficient or don't flow well at lower boost pressure (pressure ratios).

I run a true Super 40 on my 84x89 B series and it still makes 470whp at 15 psi gauge pressure (2.2 PR) at 5500 ft elevation.

As for where to buy/source them, you can pick used ones up on Diesel Forums. The 'smarter' Super 40 variant is a Holset aftermarket turbo and has a different compressor wheel and turbine wheel vs the 'production' HX40. The production HX40 will work for you though, you can also look at Goldfarb & Associates or similar on eBay for HX40's.

97civixlx

Alright thanks guys for the information

My last question is this. Or well these.

The j32a2 from the factory runs 10.5:1 from the factory. Would you run 20lbs of boost from the hx40 on this compression? I'm thinking it should be alright, a lot of people have gotten decent numbers, even 700whp. But this is my DD, so "reliability" needs to be there as well. I was going to drop the compression of the pistons by swapping them with aftermarket lower C/R pistons, because I wanted to be safe, but unfortunately I dont know how much that would affect the response of the engine or final numbers or how much "safer" it should be.

I mean, 20lbs of boost on top of 9:1 pistons (or even lower) logically seems like the response would be slower and at the same amount of boost make less power than a higher compression piston.

But then again in a noob.

TheShodan

iTrader: (14)

Don't fall for the "lower compression ratio is better for boost" thought process. It's an old style of thinking that has (luckily) long been forgotten due to better engine management tuning solutions and available fuels.
You won't have any problems running good pressure on 10.5:1 CR. Will it be exactly 20psi of boost pressure? Maybe, then again it may be 19.4psi.. Who cares. The PSI aspect is not the biggest aspect you worry about. That's for your tuner (who needs to be very competent) to decide what's the maximum boost pressure for the fuel you're using for this. That portion can't necessarily be predicted.

97civixlx

I'm glad everything checks out. Thanks again.

I was wondering lower compression for the sake of the oem rods but I guess in the end it doesn't matter. The rods are gonna get beat lol.

This set up is gonna be running on AEM V2 and it'll maybe get tuned at King motorsports in Wisconsin unless I find someone who is reputable that does etuning. I already checked with Vit Viper and AEM is something he doesn't tune do well see.

2kdrift

CR ratio wont effect the rods, your HP level / tune will

97civixlx

I'm just concerned about snapping a stock rod lol, so much so it's made me pretty paranoid. I don't think the CR will directly affect the rod, but the amount of stress the from the boost will. Yes, I know, the tune is THEE most important thing.

The oem j32a2 rods are "forged " and I say it like that because even though acura says the rods, along with the pistons are forged, many members of the acurazine community have said otherwise after opening up the engine and seeing "cast marks". The rods were forged for weight not strength they say.

Also, some people recommend NOT boosting this motor because of the "long skinny rods." Looking at the rods they really don't look too skinny compared to other Honda/Acura rods, but they are long. I don't think this really matters either though because the r/s ratio is 1.81:1 if I remember correctly so the angle of the rod is actually very good.

On j32a.com, I believe someone said they ran a 700whp civic for over 20 passes, but that means nothing to me because this isn't a race car, it's a fast DD. Is it going to be a little over kill? Probably.

There really hasn't been a ton of research done on the J engines tbough and there really isn't a lot of aftermarket support either. Custom rods and pistons cost an arm and a leg. If I was gonna spend that much money I'd jump platforms, but honda is life.

It just sucks that honda redid their engine game in 2004 and made us struggle with the fact that converting to DBW (for J series) is a pain in the *** and the ECUS for said engines monitor everything, so the won't run properly without some sort of "hack". Plus, the real deal breaker was Hondata does NOT support the J32A2 platform.

So instead of paying 650 for hondata and 350 to Vit or someone else, you gotta front the 1200 for the AEM AND get it tuned by a shop which may or may not do a good job.

TheShodan

iTrader: (14)

Your paranoia is just going to keep you up, and the difference in compression is going to be felt OFF-BOOST, not from the additional stress of the 1-2psi of boost pressure you're using. Again, it's really not going to matter for that rod.
This engine has been turbocharged many times with success. Tuning, Tuning , Tuning...

Gotta know where you're going to tune. Since you have no location on your Screenname, we can't offer suggestions.

97civixlx

The shodan says j32a2 rods are buff! 450whp capable! Lol

And I'm located central wisconsin.