Fresh compounds=high cruising egts and no top end power??

1bad93 said:
I have no clue what rpms its at, I'm not lucky enough to have the Mopar tach. But it has 35in tires with 4.10 gear set and I THINK the getrags are 1:1 in 4th. And yes its 3:01am here in good old PA lol.

posted while getting paid.
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That's still maybe 1,800rpm. Third Gear up hills, or speed up. Cruising EGT sounds ok.
 
I'm suspect of the 10psi drop after peak. Did you tack the internal gate shut or what? Do yourself a favor and put a drive pressure guage in so you know what's goin on. It'll save you a world of trouble.

As far as rpm being an issue...the 93 with tge getrag in fifth would cruise at 60 at around 1700rpm with 3.55's and 33's. I would shift to fourth or speed up on any decent hills and still only creep to 1200 degrees on a hot summer day with more fuel and a lazier twin set.
 
Build a spring gate for the hx35 and start with a heavier spring then you'd think. There is absolutely no way your twin set will run at its best without a gate to tune with.
 
mathews8pt said:
Build a spring gate for the hx35 and start with a heavier spring then you'd think. There is absolutely no way your twin set will run at its best without a gate to tune with.
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This is my plan to the dot, I was think maybe just get ahead of the ball a little and plum up a external gate from the manifold but it would a lot easier to mount up a spring style gate tune from their. And josh I that was 4th gear at about 15-20psi with my setup. No i didnt tac it shut i just mechanic wired it shut. And once I get a new larger boost gauge(I peg the 50psi gauge) I'll plum the old one into the down pipe to get my drive readings.
Jon

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How are you guys with spring style setups measuring spring tension? Or just getting the heaviest one possible? I'm going to check out the hard ware store here today and see what I can find.
Jon

posted while getting paid.
 
Drive readings dont come from the downpipe they are measured in the exhaust manifold....and youll need more than a 50 psi gauge
 
jmd025 said:
Drive readings dont come from the downpipe they are measured in the exhaust manifold....and youll need more than a 50 psi gauge
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Yea, your right Thiers my brain fart for the day.
Jon

posted while getting paid.
 
Even if you do use a spring, you'll need to gate all 6 cylinders. The stock gate only opens to 3 of them, as it is only in one volute of the turbo.
 
TURBOLVR said:
Even if you do use a spring, you'll need to gate all 6 cylinders. The stock gate only opens to 3 of them, as it is only in one volute of the turbo.
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I did drill out the divider as much as I could possibly drill open. I don't know how much of a deference it'll make but I did it when I first put the hx35 on. And does anyone have any experience with the jgs soot trap for a drive pressure gauge? Figures if I'm gonna spend the money on getting a separate 100pso gauge just for drive pressure I mine as well just make it a dedicated gauge.
Jon

posted while getting paid.
 
OK so after what you guys recommended I got a spring style waste gate on the secondary and new boost gauge, primary boost gauge and drive pressure gauge with a JDS partical trap. Well tonight was the first run. It ran a lot better egt wise, but still flat lined up top. Not as bad as before but still only seeing 40lbs total boost 60lbs of drive pressure and about 15-19lbs out of the primary witch seems low. So my question is would I want to drive the secondary harder or less? Honestly the spring on the gate isn't really that stiff(best I could find around me). I've been trying to find the equation to find secondary boost in the tuning twins thread.
Thanks Jon

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Hmmmm......what are the specs on the big charger?
 
Its a s472/83/1.10 ar on a t-6 foot.
Jon

posted while getting paid.
 
It sounds like your choking out at your hx35. You need to wastegate your secondary and spool your primary a little harder.

John
 
I am waste gating the secondary. I made a spring gate to do so. I don't know how to figure out how much boost the secondary is making tho. I know thiers a formula some were on how to figure that out I can't seem to find it now.
Jon

posted while getting paid.
 
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Do yo have 2 boost gauges? You might not be wastegating enough that's why you have high Drive pressures before your secondary, and not seeing higher boost numbers from your primary.

John
 
Yea I have two boost(total and primary) and drive. Its make 40 over all and only like 15-18lbs out of the primary. So I'm thinking the primary isnt getting driven hard enough. And its about 60lb drive pressure. Would I tighten up the waste gate and have it open later? Cause the spring I have on it now is lessened up the whole way now?
Jon

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In theory, you need to do the calculations based on pressure ratios; they should be balanced. Gauge pressure is also pressure above atmosphere, so you need to convert to absolute pressure. At sea level, it's about 14.7psi, which means you're seeing (14.7 +18)=32.7psia blowing into the small charger, which is making (40+14.7)=54.7psia.

So your pressure ratio for the big charger (32.7/14.7)=2.22:1
And high=pressure charger (32.7/54.7)=1.67:1

This actually isn't bad, normally compounds are pretty far off. For instance, my 57/71mm combo made 40psi out of the big charger, while the small turbo was barely doing anything. However, it also made 60psi of boost with 65psi of drive.

So here's my guess....on my 95, an HX35 made 42psi by itself at c.430rwhp, so I think your big charger is basically pushing enough air onto the HX35 to make its drive pressure higher, but not really enough to raise your total boost up. The atmosphere charger on my 95 is a 71/74/.85 a/r, so it's doing a whole lot more work than the big turbine wheel deal you have on there. If it were my truck, I would add some bigger injectors and more timing, and call it good.
 
Calculating @ 14.7 atmospheric pressure (not sure of elevation).

At 40 psi manifold and 15 primary:
  • 12.37 psi secondary.
Pressure Ratios:
  • 3.72 at Manifold
  • 2.02 at Primary
  • 1.84 at Secondary.

At 40 psi manifold and 18 primary:
  • 9.89 psi secondary.
Pressure Ratios:
  • 3.72 at Manifold
  • 2.22 at Primary
  • 1.67 at Secondary.

Look at the maps for each and make sure you keep the turbos in the sweet spot for dense air / max efficiency.
Hope this helps.
 
JQmile said:
In theory, you need to do the calculations based on pressure ratios; they should be balanced. Gauge pressure is also pressure above atmosphere, so you need to convert to absolute pressure. At sea level, it's about 14.7psi, which means you're seeing (14.7 +18)=32.7psia blowing into the small charger, which is making (40+14.7)=54.7psia.

So your pressure ratio for the big charger (32.7/14.7)=2.22:1
And high=pressure charger (32.7/54.7)=1.67:1

This actually isn't bad, normally compounds are pretty far off. For instance, my 57/71mm combo made 40psi out of the big charger, while the small turbo was barely doing anything. However, it also made 60psi of boost with 65psi of drive.

So here's my guess....on my 95, an HX35 made 42psi by itself at c.430rwhp, so I think your big charger is basically pushing enough air onto the HX35 to make its drive pressure higher, but not really enough to raise your total boost up. The atmosphere charger on my 95 is a 71/74/.85 a/r, so it's doing a whole lot more work than the big turbine wheel deal you have on there. If it were my truck, I would add some bigger injectors and more timing, and call it good.
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Then why would it feel like i lost a lot of power? With just the hx 35/40 and pod injectors it felt a lot faster than what it does with the compounds and 5x16s? I guess the pods didn't feel too much different till I put more timing in it.
Jon

posted while getting paid.
 
Formula:

Primary PR:
(Primary boost + atmosphere) / atmosphere = Primary PR

Secondary PR:

[(Total boost + atmosphere) / (Primary boost + atmosphere)] = Secondary PR
 
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