Laxin's Turbo Build

[laxinwarrior]

I have the J-pipe to a 90* coupler to a 60*(i think) aluminum pipe to another 90*coupler into the intercooler. It was actually really simple and straightforward. No matter what you do get the BEST quality couplers, they are ridiculously expensive but well worth it.

[seth98esT]

For the lower IC piping I used the Dejon Tool j-pipe which is almost a 180, to a 90* pipe to another 90* pipe to a third 90* pipe. For the uppder I used the stock tb elbow off a 1g, a 45* to another 45* to a 90* to the FMIC. All straight couplers, bends are all in the pipes.

[bmore303]

Oh nice. I think I'll pull some parts out the engine bay...take a few pics and sketch a rough diagram of the different setups when I get time.

Thanks Lax and Seth 8) .

[laxinwarrior]

No prob man. Anything to help out a fellow TGCer.

[laxinwarrior]

Well I should hopefully be getting to the dyno sometime in the next week to get tuned. It's going to be interesting to see how much power I gained. Here is my dyno sheet from when I was n/a with CAI only. Anyone have any predictions?

[seth98esT]

How much boost?

[kolio]

were you 5 spd at the time of the dyno or auto?

kind of helps me on what i expect to dyno Sat

[laxinwarrior]

Seth - i'll be running a stock wastegate so around 8ish but i've seen spikes up to 10-12

Kolio - I was 5 spd when I got dynoed before.

[seth98esT]

Id say 218.5whp 238.9ftlbs :)

[laxinwarrior]

I like that prediction, I was thinking I would be just shy of 200whp.

[laxinwarrior]

Well as some of you guys know I was having a high rpm misfire for the past couple days .... well went to start it up last night and it was running like shit so I went out and pulled the plugs this morning and well the plug from cylinder #2 was fucked. The insulator was cracked off from way down in the base and the electrodes are pretty messed up too. Anyways I doubt I will be getting to the dyno anytime soon but it might be a nice time to go for the DOHC swap. :?

P.S. I have pictures of the plugs but my computer is being gay and won't let me upload them so i'll try to get them up sometime soon.

Edit - Compression test: cyl 1 195, cyl 2 175 cyl 3 180 cyl 4 205

I might have jumped the gun a little bit but i'm still burning oil like crazy even at idle so im thinking it might be valve guides/seals from when the timing belt went out on me.

[laxinwarrior]

Ok well I will be replacing the valve seals shortly but it seems even more evident at this point that I blew out the turbo's oil seals. While that is an easy enough fix, it gets expensive when you factor in the reassembly and balancing. I have been throwing around the idea of upgrading turbos instead so i'm looking for some opinions on which way to go. My overall goal is to have a completely streetable built 4g64 DOHC for which i'm already collecting parts. I was thinking about something along the lines of a 20g but I would want something that would be able to spool relatively early since I don't want to have to rev the engine up past 7500-8000 max. How much of an advantage would a dual ball bearing turbo have on spool times since I haven't been able to find any numbers in my research? Basically if someone like seth or john that knows turbos pretty well could just give me a basic comparison of a 20g and a gt30r that would give me a solid idea on what i'm looking for.

[DOHCstunr]

as lng as you have the tdo5h 20g and not the tdo6 or tdo6h.... you will have a very usable turbo.

the 6 has a larger wheel and in turn moves the power up the band.

[seth98esT]

On a built 4g64, what kind of boost are you looking to run? 18-25psi?

[laxinwarrior]

Yeah most likely no more than 20-25 ... maybe 30 on race gas if i ever take it to the track. (can we say dual stage boost controller...)

[seth98esT]

Copying a post I made way back when, just adding the 20g and GT30R at 20psi, 25psi, and 30psi.


OK here goes:

Engine Volumetric Flow Equation
VAF(Volume Air Flow in cu. ft/min) = (Enging RPM x engine cid) / (1728 x 2)

So in a 2.4L

VAF = (6200 x 146.458) / 3456 = 262cfm

Ideal Gas Law/Mass Air Flow
The Ideal Gas Law is a handy equation to have. It relates the air pressure, temperature, volume, and mass (ie, pounds) of air. If you know any three of these, you can calculate the fourth. The equation is written:

P(absolute pressure) V(volume) = n(related to the number of air molecules, which is an indication of the mass (or pounds) of air) R(constant number) T(absolute temp)

Lets assume that we are at sea level.

20psi of boost(psig) = 34.7psia(14.7+20)
25psi of boost(psig) = 39.7psia(14.7+25)
30psi of boost(psig) = 44.7psia(14.7+30)

The absolute temperature is the temperature in degrees F plus 460. This gives degrees Rankine, or deg R. If it is 80 deg F outside, the absolute temperature is 80 + 460 = 540 deg R.

n(lbs/min)= P(psia) x V(cu.ft./min) x 29 / (10.73 x T(deg R))

Lets say you are running an intercooled setup and temps in the intake manifold are 130F and you are still running 20lbs, 25lbs, or 30lbs of boost:

Absolute temperature = 130 deg F + 460 = 590 deg R
Absolute pressure =
20 psig + 14.7 = 34.7 psia
25psig + 14.7 = 39.7 psia
30psig + 14.7 = 44.7 psia

For 20psi:
n(lbs/min)= (34.7 psia x 262 cfm x 29) / (10.73 x 590 deg R) = 41.65 lbs of air per minute (ideal)

lbs air per minute actual = 41.65 x 0.85 = 35.4 lbs air/minute

For 25psi:
n(lbs/min)= (39.7 psia x 262 cfm x 29) / (10.73 x 590 deg R) = 47.65 lbs of air per minute (ideal)

lbs air per minute actual = 47.65 x 0.85 = 40.50 lbs air/minute

For 30psi:
n(lbs/min)= (44.7 psia x 262 cfm x 29) / (10.73 x 590 deg R) = 51.80 lbs of air per minute (ideal)

lbs air per minute actual = 51.80 x 0.85 = 44.03 lbs air/minute


Volumetric Efficiency
If life was perfect, we could fill the cylinders completely with air. If we had 17 psi boost in the intake manifold, we would open the intake valve and get 17 psi in the cylinder before the intake valve closed. Unfortunately, this doesn't usually happen. With some exhaust remaining in the cylinder and the restriction offered by the intake ports and valves the actual amount of air that flows into the cylinder is somewhat less than ideal. The amount that does flow divided by the ideal amount is called the volumetric efficiency.

To take this into account when we calculate flow into the engine, we multiply the ideal amount of air by the efficiency to get the actual amount of air:

actual air flow = ideal air flow x volumetric efficiency

Now the lower your FMIC/cooling system can cool the air by the time it hits the intake manifold, the more lbs air/min you will move. So an intercooled turbo setup vs a non-intercooled setup will vary greatly!

Compressor
The compressor is the part of the turbocharger that compresses air and pumps it into the intake manifold. Air molecules get sucked into the rapidly spinning compressor blades and get flung out to the outside edge. When this happens, the air molecules get stacked up and forced together. This increases their pressure.

It takes power to do this. This power comes from the exhaust side of the turbo, called the Turbine. Not all of the power that comes from the turbine goes into building pressure. Some of the power is used up in heating up the air. This is because we lowly humans cannot build a perfect machine. If we could, all of the power would go into building pressure. Instead, because of the design of the compressor, the air molecules get "beat up", and this results in heat. Just like rubbing your hands together will warm your hands due to the friction between your hands, the friction between the compressor and the air and between the air molecules themselves will heat up the air.

If you divide the amount of power that goes into building pressure by the total power put into the compressor, you get the efficiency of the compressor.

For example, if the compressor is 70% efficient, this means that 70% of the power put into the compressor is used in building air pressure. The other 30% of the power is used heating up the air. That is why we like high efficiency compressors; more of the power is being used on building pressure and less is used heating up the air. You want to be in the 65% and higher efficiency range.

How to read a compression map(that I posted above)
Figure out the pounds of air that you are moving through the engine. We are passing 29.77 lbs/min of air, at inlet conditions of -0.5 psig and 70 deg F. Now correct that flow to the standard temperature and pressure.

Corrected flow = (actual flow x (Tin/545)0.5) / (Pin/13.949)

The standard temperature is 545 deg R, or 545 - 460 = 85 deg F.

o we are correcting the flow from 70 deg F and -0.5 psig to 85 deg F and -0.75 psig.

Tin = 70 + 460 = 530 deg R
Pin = -0.5 + 14.7 = 14.2 psia

0.98614251719524976895424215738132

1.0179941214423973044662699835114

Corrected flow for 20psi = (35.40 x (530/545)^0.5) / (14.2/13.949) = 34.29lb/min

Corrected flow for 25psi = (40.50 x (530/545)^0.5) / (14.2/13.949) =
39.23lb/min

Corrected flow for 30psi = (44.03 x (530/545)^0.5) / (14.2/13.949) = 42.65lb/min

Now for Mitsu maps, they use CFM, Garret uses lb/min. Every 10 lb/min is equal to 144.72 cfm. So:

CFM = (34.29 lb/min / 10) * 144.72 cfm = 496 cfm for 20psi
CFM = (39.23 lb/min / 10) * 144.72 cfm = 568 cfm for 25psi
CFM = (42.65 lb/min / 10) * 144.72 cfm = 617 cfm for 30psi

So we mark that point on the bottom of the graph, and draw a straight line upward from that point.

The next step is to figure out the compression ratio, using absolute pressures. Using our example, we had 8 psi boost in the intake manifold. Let's suppose the pressure drop from the turbo outlet to the manifold is 3 psi; so the actual compressor outlet pressure is 3+20=23 psig. The air pressure is 0 psig, but since the turbo is sucking air to itself the pressure at the inlet is lower than that. Let's say it is -0.5 psig at the inlet. Then the compression ratio, Pout/Pin is :

20psi Pout/Pin = (23 + 14.7) / (-0.5 + 14.7) = 2.65
25psi Pout/Pin = (28 + 14.7) / (-0.5 + 14.7) = 3.01
30psi Pout/Pin = (33 + 14.7) / (-0.5 + 14.7) = 3.36

So then we find about where 2.65/3.01/3.36 are on the left side of the graph and draw a line horizontally from that point. Where the two lines meet is where the turbo will operate.

SO using my 1337 skills in MS Paint:

Small 16g isnt really efficient at all over 20psi on a 4g64. Its at about 68% @20psi and is off the graph at 25psi and way off at 30psi. So probably after 22ish psi, you will stop making power.


TD06 20g is at ~75% @ 20psi. Same design as the 16g, just bigger. I forget if the 20g uses the same compressor wheels as the 16gs or not. Again not too efficient past 25psi.


GT30R, kind of a hard map to read. Looks like 76% @ 20psi, 74% @ 25psi, and 70%@30psi?


With all that said, Id say go with a GT30R! I couldnt find a good map for the GT35R for some reason. I am bored, I will find one. Yes.

[seth98esT]

Found one. Probably not a good turbo to use unless you do some headwork/transwork to rev above 6200rpm. The turbo probably woudl spool at 4000-5000RPM, so wouldnt be too much fun in that area.

[laxinwarrior]

Ok well right now i'm sort of torn between two options. I can get a Garrett 60 trim with BB center cartridge for $1079 or a gt30r for $1205. Not really sure if there is a big enough difference in the two to warrant spending the extra couple hundred. :?

Oh and Seth thanks for those compressor maps they helped out a hell of a lot.

[run1206]

wow, before i was a lil confused about reading compressor maps, now i understand it, thanks laxin and seth!!

[bmore303]

I nominate Laxin to do the first destroked 2.1L 4G64 in a 7G. GT35R would be pretty fun on that .