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Old 03-25-2005, 10:35 PM   #1
RiftsWRX
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Default Turbochargers: when less is more...

This is actually a continuation of a conversation some of us were having in PPB about how one turbo running 26 PSI made almost 50 HP less then one running near it's optimal "sweet spot".

I've been aggressively tuning the SBR GT30R-11 I have to find a decently acceptable blend of performance vs. output on Chicagoland's 93 octane fuel.

Starting at 23 PSI I've progressively tuned down the boost due to the inability to carry any decent level of ignition timing. The failure to do this has resulted in EGT's reaching near 1700F.

Code:
ECT	MAP	RPM	MPH	Timing	MAF-g	MAF-v	IDC	KC	WDC	Load	
1st gear
174	4.6	1055	2	21.5	4.28	1.28	1.58	0	0	0.47	  
174	4.8	945	2	13	5.01	1.4	1.41	0	0	0.53	  
174	8.4	966	3	21.5	10.92	1.76	2.68	0	0	1	  
174	9.4	1504	3	19.5	12.66	1.82	4.17	0	0	1.03	  
176	8.7	1749	4	25	14.21	1.88	4.85	0	0	0.97	  
176	10.3	1814	4	23	22.35	2.32	7.74	0	3.9	1.44	  
176	13.2	2278	4	19.5	30.65	2.38	9.72	0	9.8	1.59	  
176	13.2	2577	4	19	37.35	2.5	11.54	0	18	1.72	  
176	13.5	2626	6	18.5	40.01	2.58	11.76	0	25.9	1.81	  
176	15.8	2870	6	23	53.35	2.76	15.31	6	32.2	2.19	  
176	16.7	3142	8	29.5	63.39	2.9	18.1	10	40	2.38	  
176	18.1	3332	8	31	71.64	3.08	20.61	10.5	47.8	2.59	  
176	19.7	3634	11	30	89.88	3.28	24.03	11	54.1	2.91	  
176	21.3	3904	11	27.5	114.67	3.52	32.48	10	62	3.31	  
176	24.5	4422	16	23.5	145.84	3.8	47.17	10.5	67.8	4	  
176	27.7	4883	20	18.5	183.23	4.16	67.71	8	76.1	4.66	  
176	31.6	5361	20	12	225.2	4.32	78.91	6.5	80	5	  
176	33.8	5756	26	11.5	239.17	4.4	85.95	5.5	83.9	4.84	  
176	34.8	6308	26	17.5	242.68	4.42	86.12	5	84.3	4.53	  
176	34.5	6843	32	19	245.79	4.44	86.13	4.5	84.7	4.31	  
2nd gear
176	35	5285	32	11.5	224.78	4.3	0	6	85.9	5.19	  
176	36.9	4947	39	8.5	220.14	4.3	78.1	6.5	85.5	5.41	  
176	36.6	5119	39	9	226.89	4.34	79.72	6.5	85.5	5.38	  
176	35.8	5263	44	9.5	232.4	4.36	80.84	6	85.9	5.25	  
176	35.4	5384	44	9.5	236.63	4.4	82.69	5.5	87.5	5.22	  
176	35.1	5547	49	9.5	238.75	4.4	84.02	5.5	88.6	5.13	  
176	35	5652	49	9.5	241.35	4.42	85.61	4.5	89.8	5.06	  
176	35	5837	54	10.5	244.45	4.4	83.42	4.5	91.4	4.91	  
176	35	5948	54	12	243.13	4.42	83.74	4.5	92.2	4.81	  
176	35	6142	59	13.5	243.57	4.42	85.17	4.5	92.5	4.72	  
176	34.8	6260	59	16.5	244.01	4.42	85.47	4.5	91.4	4.63	  
176	34.8	6477	64	17	244.9	4.44	85.66	4	91	4.53	  
176	34.7	6399	64	17	246.23	4.44	0	4.5	90.6	4.78	  
3rd gear
176	37	4829	67	8.5	211.35	4.28	74.18	7.5	90.2	5.34	  
176	36.6	5092	67	8.5	224.78	4.3	79.29	6.5	90.2	5.31	  
176	36.4	5130	71	9	227.74	4.32	78.79	6.5	90.2	5.31	  
176	36.1	5201	71	9	226.47	4.34	79.88	6.5	91	5.28	  
176	36.1	5234	74	9.5	229.43	4.34	80.39	6	92.2	5.25	  
176	35.8	5263	74	9.5	233.24	4.36	80.84	6	92.9	5.22	  
176	35.5	5327	78	9.5	233.67	4.36	81.82	6	93.7	5.22	  
176	9.4	4396	78	9.5	53.9	2.44	0	0	0
What's interesting to note is the airflow of the turbo.

As you can see we're not really exceeding beyond ~245 g/sec of air, and timing never exceeds beyond 17 degrees of advance.

The "sweet spot" on this turbo is 18.4 PSI. What i've noticed is that at that level I could run close to 21 degrees of advance, but airflow dropped to a peak of 232 g/sec. Doesn't sound like much, but on a bigMAF like I'm running that's actually significant.

To give you an idea of just how tempermental and exact turbocharger PR's can be in regards to performance, check this out....

Code:
MAP	RPM	Timing	MAF-g	MAF-v	IDC	KC	WDC	Load	
1st gear
12.6	1870	34.5	35	2.44	7.98	0	5.9	1.63	  
15.1	2583	31.5	40.39	2.6	12.12	0	14.1	1.88	  
15.8	2929	29	52.13	2.74	15.62	2	20	2.09	  
16.7	3108	27	60.04	2.86	17.24	3.5	27.8	2.22	  
17.8	3782	14.5	77.1	3.12	22.59	6	34.1	2.53	  
20.7	4096	23.5	106.11	3.44	33.2	6	42	3.06	  
23.2	4529	21.5	139.36	3.84	51.21	8	49.8	3.75	  
26.6	4960	20	192.21	4.12	65.6	9	56.1	4.41	  
30.9	5665	14.5	226.47	4.34	82.17	8	60	4.78	  
33.4	6088	16.5	240.46	4.42	87.01	7	62	4.63	  
34.2	6806	20	246.23	4.44	88.56	6	62.4	4.34	  
34.2	6824	20	248.45	4.32	0	6.5	62.4	4.53	  
2nd gear
35.5	4515	10.5	209.8	4.26	72.24	7	59.6	5.41	  
36.3	5061	10.5	223.08	4.32	78.81	8	56.5	5.31	  
35.5	5271	11.5	222.66	4.3	78.71	8	54.9	5.13	  
34.2	5407	12.5	228.16	4.36	79.59	8	54.9	5.06	  
34	5474	12.5	230.7	4.36	80.58	8	55.7	5.03	  
33.8	5682	13	234.51	4.36	82.42	8	56.9	4.91	  
33.8	5827	15	232.82	4.36	82.05	8	58	4.78	  
33.7	6063	16.5	239.17	4.4	82.78	7.5	58.8	4.72	  
34	6178	16.5	239.17	4.4	81.71	7	59.6	4.66	  
34	6334	19	240.46	4.4	82.43	7	60.4	4.56	  
34	6438	19.5	242.24	4.42	81.03	6.5	61.2	4.5	  
33.8	6510	20	242.24	4.42	0	6.5	61.6	4.53	  
3rd gear
35.8	4641	10.5	207.43	4.28	71.29	7.5	59.2	5.34	  
36	5158	11.5	223.08	4.32	75.93	8	56.9	5.13	  
34.8	5183	12.5	225.2	4.32	76.29	8	56.5	5.16	  
34.7	5205	12	224.35	4.32	76.61	8	56.1	5.13	  
34.4	5274	12.5	225.2	4.32	76.51	8	55.7	5.13	  
34.4	5346	12.5	225.2	4.32	76.41	8	55.7	5.09	  
34.1	5403	12	233.36	4.36	79.54	8	56.5	5.13	  
34.1	5435	12	233.78	4.36	80	8	56.9	5.09	  
34.1	5498	12.5	230.37	4.34	78.59	8	57.3	5.03	  
34.1	5601	12.5	233.78	4.36	81.25	8	57.6	5.03	  
34	5601	12.5	234.21	4.36	80.06	8	58.4	4.97	  
34	5734	13.5	234.21	4.36	80.73	8	58.8	4.94	  
34	5800	14	234.64	4.36	80.43	8	59.6	4.88	  
34.1	5846	14.5	238.05	4.4	81.06	8	60	4.88	  
34.1	5859	15	240.18	4.4	81.25	5.5	60.8	4.88	  
34.1	5896	13	241.91	4.4	81.76	5.5	61.2	4.91	  
34.1	6000	14	238.48	4.4	80.64	5.5	61.2	4.78	  
34.2	6005	14	240.18	4.4	80.7	5.5	61.6	4.81	  
34.1	6063	16.5	241.47	4.4	80.19	7.5	62	4.69	  
34.1	6168	16.5	242.34	4.4	81.58	7.5	62.4	4.69	  
34.2	6229	19	241.48	4.4	81.06	7	62.7	4.66	  
34.2	6214	19.5	242.34	4.4	80.86	7	62.7	4.63	  
34.2	6329	19	243.23	4.42	82.36	7	62.7	4.63	  
34.1	6350	19.5	242.79	4.4	81.28	7	62.7	4.59	  
34.2	6372	19.5	242.81	4.4	81.56	6.5	62.7	4.56	  
34.2	6405	19.5	245.02	4.42	81.98	6.5	63.1	4.53	  
34.1	6432	19.5	242.79	4.4	80.96	6.5	63.1	4.5	  
34.7	6465	19.5	245.47	4.3	0	7	63.5	4.69	  
4th gear
36.3	4857	9.5	211.84	4.26	70.46	8.5	60.4	5.13	  
34.8	5201	12	223.97	3.46	65.46	8.5	37.3	4.28	  
7.1	4096	9.5	31.76	2.34	0	0	0	1.72	  
5.8	4041	11.5	5.28	1.38	0	0	0	0.16
Peaking around 245 g/sec, and almost 20 degrees of advance at about 19.8 PSI.

That's it... +- 1 PSI from ~19.5 has lead to a significant drop in power on the low side, and a significant increase in engine load and heat, without really producing power.

So next time people think that cranking a turbo is the best thing you can do, take into account the optimal breathing capacity and range of your setup, and do some tests before just cranking the motor and assuming that tuning around a PR is the way to safe, RELIABLE power production.

EDIT: oh yeah.. an EVO was given a horrible spanking in the process of producing this last log

Jorge (RiftsWRX)
www.ProjectWRX.com
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Last edited by RiftsWRX; 03-25-2005 at 10:50 PM.
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Old 03-25-2005, 10:41 PM   #2
T3RMIN4L
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jorge can you speculate as to what the same setup with an external gate as well as the same 11 cart with a roatated garrett setup would do when efficiency would rise?
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Old 03-25-2005, 10:48 PM   #3
RiftsWRX
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Quote:
Originally Posted by T3RMIN4L
jorge can you speculate as to what the same setup with an external gate as well as the same 11 cart with a roatated garrett setup would do when efficiency would rise?
I think an external gate would be pretty profound. If you think about it, the fact that gas is being diverted away from the volute all together, that effectively makes it act like a larger AR housing, as you're not cramming gas flow through it, or causing turbulance and cavitation that would throw off the rhythm of gas flow through the volute, and ultimately the turbine.

That's the biggest reason turbos like greens react so well to an external gate. The relatively small AR of the hot side is augmented by a flow diversion away from the volute and turbine.

Jorge (RiftsWRX)
www.ProjectWRX.com
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Old 03-25-2005, 10:50 PM   #4
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I got 20 on your shiny new EWG setup and a retune to compare against tommorrows results. Also, as I asked in the last thread, do you plan on doing runs with both the higher boost/lower timing and lower boost/higher timing maps?
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Old 03-25-2005, 10:55 PM   #5
RiftsWRX
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Honestly, no.

As I stated in the SBR thread, the key was a "reliable tune".

Not saying that this last tune is something most people will want to comfortably run, but comapred to the lower timing map, this one begins to leave a warm and fuzzy feeling in my tummy.

In short: no.

Jorge (RiftsWRX)
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Old 03-26-2005, 02:26 AM   #6
SaabTuner
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I don't think it's as much the turbocharger's sweet-spot as it is the engine's sweet-spot. The backpressure from a particular setup just moves the sweet-spot around slightly.

At some point the required retard in ignition, to compensate for the extra mass-flow, causes more power loss than the increased mass-flow causes power gain. Or, as in some cases, the EGT simply goes too high, despite making more power.

Someone needs to make a set of Subaru heads with Inconel exhaust valves. Raising the EGT limit to 1850*F would increase the power potential of many setups, especially on pump gas.

Adrian~
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Old 03-26-2005, 07:43 AM   #7
RiftsWRX
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Hey Adrian, long time bud.

What do you think? I've bounced this off a lot of other tuners (and not just Subaru), on just how far they'd be willing to push EGT. The overall general opinion is <1700F peak on a daily driven map. No more then 1650's on a road race type setup.

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Old 03-26-2005, 10:55 AM   #8
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Quote:
Originally Posted by SaabTuner
I don't think it's as much the turbocharger's sweet-spot as it is the engine's sweet-spot. The backpressure from a particular setup just moves the sweet-spot around slightly.

At some point the required retard in ignition, to compensate for the extra mass-flow, causes more power loss than the increased mass-flow causes power gain. Or, as in some cases, the EGT simply goes too high, despite making more power.

Someone needs to make a set of Subaru heads with Inconel exhaust valves. Raising the EGT limit to 1850*F would increase the power potential of many setups, especially on pump gas.

Adrian~
dumb question comming here,

but i know the vw guys use inconel a fair bit, especially APR, and that a few supercars use the stuff (McLaren F1 for exhaust manifolds), but i am very curious ballpark as to how much such a setup might cost to impliment. Perhaps it is the cost that is prohibitive, or more the fact that nobody has dreamed up such a setup before...

Your idea is totally new to me, which is why i ask..
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Old 03-26-2005, 07:24 PM   #9
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Quote:
Originally Posted by RiftsWRX
Hey Adrian, long time bud.

What do you think? I've bounced this off a lot of other tuners (and not just Subaru), on just how far they'd be willing to push EGT. The overall general opinion is <1700F peak on a daily driven map. No more then 1650's on a road race type setup.

Jorge (RiftsWRX)
Well, there are other things to consider too, such as how well the heads dissipate the extra heat, and whether your turbine is designed with high EGT in mind. But I think that no one has really tried going much past 1600-1700. When was the last time you heard of someone chalking their exhaust valves?

With standard stainless valves, 1750 is probably the conservative limit. It could be pushed further with the use of a 2000*F ceramic coating ... without changing the valves. Then you'd be looking at an 1850*F. Inconel, or Nimonic, as my car uses, could push that number to about 1950*F without fear of a coating failure. In practice I think Inconel is far better than a ceramic coating on moving parts like valves.

A "normal" completely stock EGT on the Viggen is anywhere between 1850-2000 degrees fahrenheit. Nimonic is a very tough alloy ... but the cyllinder head coolant passages are very different from an EJ motor.

And that's the real question mark here; can the EJ heads take the heat? If not, ceramic coat the exhaust ports (valves too, if you trust the coating) and you are good to go. You might also consider coating the turbine wheel, or at least the housing itself, to reduce the turbocharger's bearing temperatures.

A GOOD set of 8 Inconel (XH-432 stainless) valves for a Chevy big-block V8 is around $345: http://www.flatlanderracing.com/manb...ymarine38.html

You could probably get them machined to whatever spec you needed for not too much. Probably cheaper than totally custom valves anyway.

Adrian~
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Old 03-26-2005, 07:27 PM   #10
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You also may be able to buy Inconel, Waspalloy, or Haynes Alloy-X, cores from www.aerospacemetals.com .... and have them machined to your spec for cheaper still.

Adrian~

edit: In fact, Haynes Alloy-X is one of my favorites. It has a rated max service temp of 2000*F! Good match for a 2000*F Jethot coated exhaust port.

edit (part deux): When I said that the Saab tuners like to stay around 1750*F, that is on a map which is designed to survive racing (from Hirsch tuning, which gives you a warranty) ... and that's on standard stainless valves, not Nimonic/Inconel. I've seen 9000 Aero's pushing 1850*F on stainless valves for tens of thousands of miles without issue. Even one or two track days. But it's risky.

I just don't know about these Subaru heads ... but a set of WRX heads isn't too much and might be worth experimenting-on for some intrepid soul.

Good to see you as always, too, Jorge.

Last edited by SaabTuner; 03-26-2005 at 07:57 PM.
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Old 03-29-2005, 01:40 AM   #11
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Default From the SR55 dyno thread

Oops, I posted this quote in the other thread and then noticed a new thread had been started. Here's what I had posted -

Quote:
Originally Posted by RiftsWRX
It actually makes a LOT of sense.

I'm finding this out as I'm road tuning the SBR -11.

I know 18.5PSI is the sweet spot for the turbo (cause Mike's shared the compressor map with me), but I've gone as high as 23, and have been tuning down the boost since because I've realized that I'm not moving any more substantial amounts of air for the BP/EP and heat being generated. My last build this morning was 20PSI and I dropped 30F on EGT and am running an extra 2 degrees of timing. So this build I'm going to flash in when I get home is going to be the actual 18.53 PSI the map calls for and an extra 2 more degrees of timing.

I've only lost < 6 g/sec going from 23 to 20PSI.... what does that tell you?

Jorge (RiftsWRX)

www.ProjectWRX.com
Just a quick look at that map (turbine aside) 18.5 is a sweet spot maybe for redline (7k) but in the midrange that's WAY off from what it would be capable of. Yeah yeah, I know we're talking paper here but still. Plus those small Subaru style hotsides aren't doin' anyone a favor, especially with an internal gate only further aggrevates the problem.

You can see that it's actually capable of PR's over 2.72 at 5k rpms. That's moving a good bit of air for the mid range at nearly 38lbs/min. At 7k rpms, yeah, 18-20psi is a fair target. What I don't get is based on the pic of the SR40, that turbo has 7 comp blades where the GT's have only 6. I thought these things were GTBB based? I'm almost inclined to say it's the TO4B 62-1. The maps are extrordinarily close. If the APS map was skewed then...

T
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Old 03-29-2005, 06:51 AM   #12
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I think what is happening here is loss of VE at high RPM as the boost is raised because of skyrocketing backpressure. The reduction in VE almost makes up for the additional intake pressure.

Two ways to solve that without changing the turbo itself (IMHO):

1) External gate to lower backpressure at higher revs and allow you to flow more air without higher over PR. No sense in wasting any of that compressor map.

2) Reduced valve overlap in the camshafts so that the VE is less-affected by the increasing backpressure. Lots of factory cars are setup like this, but it's generally counter-intuitive for a performance car. It would still work as long as the engine can handle the added heat. (Not the best idea for a Subaru, but hey, just thought I'd toss it out here.)

Number one is clearly the easiest and, yeah, that tiny hot-side really isn't doing us any favors here. :P

It'd still be cool to see someone try number two ... just because I don't think anyone has with a Scooby motor. But why be unique when you can be t3h fast4r!!11oneone

Adrian~
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Old 03-29-2005, 07:15 AM   #13
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Someone explain number 1 to me. Isn't the exhaust gasses going through the turbine what's creating the backpressure? Even if there's an external gate, if the pressure the turbo is pushing is the same, won't the turbine still create the same backpressure on the engine? I'm lost.....

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Old 03-29-2005, 07:17 AM   #14
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Actually, thinking about it again, you probably just reached choke-flow through that small turbine housing. It might be more responsive to more boost at a lower RPM (lower exhaust volume flow at higher pressure) if you have enough octane, mechanical or chemical, to use the boost. Worth a thought.
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Old 03-29-2005, 07:20 AM   #15
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Quote:
Originally Posted by hippy
Someone explain number 1 to me. Isn't the exhaust gasses going through the turbine what's creating the backpressure? Even if there's an external gate, if the pressure the turbo is pushing is the same, won't the turbine still create the same backpressure on the engine? I'm lost.....

hippy
The external gate usually dumps into the atmosphere, which makes the turbine more efficient since it doesn't have that bypassing gas interfering with the turbine's dump-tube (your exhaust).

Sometimes the placement of the wastegate further up the header/UP, where the gas is moving more slowly, allows it to work more efficiently.

Bleeding the excess exhaust gas in an efficient manner does worlds for reducing backpressure ... and internal-gates are RARELY efficient.



Adrian~
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Old 03-29-2005, 07:41 AM   #16
mhaythor
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Can't you just get a blow-off valve?

(lol, ducking to avoid the wild flogging that half of this board is preparing to give)
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Old 03-29-2005, 08:13 AM   #17
tmarcel
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Quote:
Originally Posted by hippy
Someone explain number 1 to me. Isn't the exhaust gasses going through the turbine what's creating the backpressure? Even if there's an external gate, if the pressure the turbo is pushing is the same, won't the turbine still create the same backpressure on the engine? I'm lost.....

hippy
What Saabtuner said is right on. To put it in even more lay terms, you can think of the external gate on a turbo with a smallish hotside as performing as if it's got a larger AR. As soon as peak pressure is reached that gate pops open, dumping out and bypassing the turbo. The turbo is still partially in the stream so it keeps the manifold pressure up. However, it's using just a little exhaust energy at this point since it's already spinning and a lot of the backpressure is now relieved. Hope that clarifies a little further.
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Old 03-29-2005, 08:18 AM   #18
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Quote:
Originally Posted by mhaythor
Can't you just get a blow-off valve?

(lol, ducking to avoid the wild flogging that half of this board is preparing to give)

Blow off valve is on the wrong side of the engine and is used for a different pupose. It prevents surging between shifts or when you let off the gas. Surging is when the turbo is physically trying to cram more air than the engine will allow into the intake. When this happens the compressesd air is sent sailing back and forth between the comp housing and the intake manifold. This is bad and damaging to the turbo for the short of it.
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Old 03-29-2005, 08:23 AM   #19
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Quote:
Originally Posted by SaabTuner
... and internal-gates are RARELY efficient.



Adrian~
Not always. There are some very well designed internal set ups. There are race teams using internal gates on high dollar road track cars and Garrett makes some internal gate turbos that work quite well. The GT32 works great as I've got first hand experience with them on at least two cars now - both using even larger comp sides so the part in question, the hotside, functions very well with the internal gate. Plus the 32 gate is facotry new with a 18psi spring.

T
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Old 03-29-2005, 08:35 AM   #20
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Quote:
Originally Posted by tmarcel
Not always. There are some very well designed internal set ups. There are race teams using internal gates on high dollar road track cars and Garrett makes some internal gate turbos that work quite well. The GT32 works great as I've got first hand experience with them on at least two cars now - both using even larger comp sides so the part in question, the hotside, functions very well with the internal gate. Plus the 32 gate is facotry new with a 18psi spring.

T
You're right; there are some good internally gated hot-sides. That's why I said rarely, and not never.

It would still be slightly more efficient with an external gate, iff that EWG dumps to atmosphere. But that's sort-of cheating, since it bypasses any muffler-restrictions.

Adrian~
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Old 03-29-2005, 08:56 AM   #21
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ok, i tried this out, and fwiw, on my sr50, i dropped my boost down to 19psi from 22psi and saw .1 to .2 less MAF volts over the same range. the sweet spot for my turbo definately isnt 19psi.
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Old 03-29-2005, 08:57 AM   #22
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Adrian,

Yeah I guess we were on the same page and didn't even know it Seriously though, it's just kind of sad that you've got to spend a ton of cash on a turbo only to find out that you would be far better off to add on an EWG (in addition to what you've already got). Only prob is, and like you said, is that dumping the exhaust straight below the car like that is unbearable for most folks. Functionally, it works well for power but has some inherent draw backs. For me (and many, many others) this won't work for a DD car. I've got a kit that will come out soon (been in the making since last August) with the above mentioned turbo. Just in different configs than the standard off the shelf GT32 offers. I will show you that teh internal gate, high tensioned 18psi threshold, can work well and is a lot more streetable than the EWG route.

Todd
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Old 03-29-2005, 09:20 AM   #23
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Quote:
Originally Posted by happasaiyan
the sweet spot for my turbo definately isnt 19psi.

happasaiyan,

That's a little generalized don't you think? Where's this "sweet spot" at? 4k, 5k, 6k, redline?? Please boost it up in the mid range and tell us what happens with your maf v. I was curious so I plotted some numbers without a pressure drop. You can see that it's effiecient way beyond 19psi.

[IMG][/IMG]
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Old 03-29-2005, 09:38 AM   #24
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well...my boost was 23psi midrange -> 19-20 at redline

i changed it to ~19 from midrange to redline

for example, on my old boost map, i would get 4.5V from 4500rpms. with the revised one, i dont get 4.5V until a little over 5000rpms. i couldnt get any redline runs...as traffic sucked yesterday. so technically, according to that map, i was running pretty efficient with my first boost map, yes?
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Old 03-29-2005, 09:44 AM   #25
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Quote:
Originally Posted by happasaiyan
ok, i tried this out, and fwiw, on my sr50, i dropped my boost down to 19psi from 22psi and saw .1 to .2 less MAF volts over the same range. the sweet spot for my turbo definately isnt 19psi.

I did the same. My turbo likes to run in the 20-22psi range. by this I mean 20-22 from 3800 rpm to 6000 rpm droping into the 19psi range at redline. I drop the boost by design. I'm also runing fairly low timing 17-18 degrees up top as I have not really experimented with adding more fuel and timing to offset any potential det.
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