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High flow are still a restriction I think pure motorsport cats used in FIA racing series are 100 cell. For ultimate performance, completely open exhaust. The turbine is a pressure multiplier. So whatever the backpressure in the exhaust is, it gets multiplied by the pressure ratio of the turbine operating point.
There is a restriction, but HJS cats flow 90-95% as well as a straight pipe, that’s why racers pay the big bucks for them.
Cheap metallic cats from China are bound to get clogged and/or fail from heat. They do very little other than muffler the sound. I have doubts your HJS cats are clogged unless you’ve been running a super rich tune for a very long time. Even OEM cats which look to be around 600 cell are not getting clogged.
The catless pipes will probably give you 10-15 whp over your HJS cats, so it seems unlikely that’s the bottleneck.
Is it possible the even larger exhaust turbine wheel is oversized for the stock frame turbos? I think Vektor is on to something with boost control. You may have to ditch the internal gates and have a custom external wastegate setup.
I scooped up Vektor’s prototype set
and have the externals capped off because I had a feeling it may be needed down the road.
I completely agree that even a HFC will be a potential restriction, but I meant to say that I thought that the HJS HFC would have been able to support the powers that @4 Point 0 is hoping to put down.
Following this closely, as post warranty I hope to follow in the footsteps of the current trail blazers
As others have pointed out, there is always a limit to hybrid turbos. The GTS turbine housings where sized for 225hp each and now you are at 400hp. Asking for almost double the power out of them is about as much as you can expect. There is a thread in the 996 Turbo section of a guy with Garrett G-series turbos. He started out with G25-660 and upgraded to G30-770. Pure track car. Cayman chassis with 3.8l turbo engine of I recall.
Could Tial make a high performance intercooler with the PWR rolled tube core? CSF has one for the 992 Turbo they claim reduces heat soak. I'd be a customer
Thanks for all the replies guys.
I had thought of this. PWR are less than an hour from my place. I have the PWR centre radiator, and i will get around to replacing the front side two with PWR as well. It gets hot here.
TiAL have already done the work. Their I/C has 2.5 outlet on the end tank. Stock and my AMS are only 1.9 I believe.
So is the question more about flow or cooling?
If its just flow, than easier to just order the TiAL I/C.
I was aiming for 100-130hp more than where I was on stock turbo’s.
I have achieved 42hp so far, but remember I have only increased boost by 1psi. I’m still on E40 as well. But there is little gain from E40 to E85.
I’m looking into a HTG (TCU replacement). It may a lot of time consuming work to get it to work with Stock ECU. Whereas if I did a MoTeC ECU replacement first, then the HTG would be far simpler.
But again, I don’t really want to spring for a one off MoTeC. We need them to do a kit as it will halve the cost.
Tyler has heat-soak issues like we do with the AMS's, not sure if it's to the same extent. My car is definitely pulling power after 2 -3 laps. In hot weather, I'll see a decrease of up to 4mph in the straights. He's running a lower boost ( I guess than his 1/4 mile tune) and E85 to keep the IAT's down.
I second water/meth injection. I see ridiculous temp differences when the meth kicks in vs without (and I currently have stock intercoolers). I want to say 50+ degree differences from what I can recall.
In regards to flow bottlenecks, I don’t think the smaller diameter of AMS inlets/outlets are going to free up much if any power. There will always be a restriction, and the turbine and compressor housings are where it all starts. Like I said, these are stock frame turbos
albeit larger GTS frames - but they’re not flow monsters. These are very small turbos with very large wheels.
I think you need to figure out what the compressor map looks like on the M800’s to see the efficiency range of the turbos. If they’re pushed beyond their efficiency range and you’re not making more power with more boost, that’s a sign you may be tapped
out. You can squeeze more out with better IAT’s and denser, cooler air - use meth injection, etc. to get more power, but I think you need to set your power expectations on stock frame hybrids.
140 MPH trap speed is a better indication.
BTW, we dyno with no fans.
I am looking at an additional 58-88hp at the wheels from where i am now. Basically 100-130hp delta from stock turbo’s.
I believe there is a choke point that is holding the car back.
On the 26th Nov I will be catless and back on the dyno.
140 mph trap speed would need about 700 to the wheels on ethanol or race gas. I’m sure you’ve already seen APR hit those trap speeds with the 660’s in not so ideal conditions (very hot day).
Curious what fuel you’re using? Are you blending ethanol or using race gas?
Next time you’re at the dyno, have a cheap hand pressurized plant sprayer with ice and cold water and spray down your intercoolers (from the bumper outlets). Without airflow or cooling, any air to air IC is going to get heat soaked - so spraying them with water (if allowed by the dyno operator) is better than nothing.
You'll heat soak the crap out of everything super fast with no fans/blowers. This first pic is from 2016, one of our first dyno sessions with our 991.2. I do NOT recommend doing this! but we saw a significant difference in dyno/ECU feedback. This crazy test with Home Depot blowers is what led us to make our own top rear industrial blower setup specific for 911 applications. Not only did it skew results more in the direction of actually moving through air, it allowed for continuous testing whereas before you could only do so many pulls before everything was just too H-O-T... even with 55mph of air hitting the front of the car, without the rear blowers it soaks. The point is, your dyno results may not reflect reality. You'll be left with drag results to measure increases, which isn't bad, it just doesn't paint a clear picture of how and where you're gaining power. Anything you can spray onto the I/C during testing or even a leaf blower would be better than nothing
Last edited by VektorPerformance; 11-11-2021 at 10:06 AM.
140 mph trap speed would need about 700 to the wheels on ethanol or race gas. I’m sure you’ve already seen APR hit those trap speeds with the 660’s in not so ideal conditions (very hot day).
Curious what fuel you’re using? Are you blending ethanol or using race gas?
.
I use blend 50% E85 / 50% 98RON (93OCT) I call it E40, but I guess its really E42.5 LOL. We round and call E40. Been running that for at least 3 years Solidly.
I don’t want to get into American Dyno numbers vs Australian or ROW dyno numbers. But with conversion accounting for this, I believe i am about 58hp short of where Tyler is at present. When i believe we have achieved this extra 58hp, I’ll go to the strip and see if i can get 140MPH as proof.
Originally Posted by VektorPerformance
The point is, your dyno results may not reflect reality.
Yes, we understand this. I’ll send him these pics and see if we can rig something up for next time.
I am having shift issues 3rd to 4th. Thats going to need to be addressed at some point. Maybe HTG.
OK....so I vowed to slow my modding down and then I start reading your posts...damnit. I already have APR tune and the HFC's which made a HUGE difference in sound and HP but looking to tweak the car some more. After reading it looks like IPD plenum and maybe all the TiAL plumbing? What are your thoughts, where did you get all this stuff, what is involved in changing it up and do I need a re-tune afterwards? I don't even know if my APR static tune would even be effective. I used to do a lot of conversions and add-ons but this power escalation under the guise of a Targa 4 GTS is exciting. I already have taken a few cars and left them in the dust with jaws on the ground but want a little more! OK OK...more more...HA!
11-07-2021, 02:04 PM
I think pure motorsport cats used in FIA racing series are 100 cell. For ultimate performance, completely open exhaust. The turbine is a pressure multiplier. So whatever the backpressure in the exhaust is, it gets multiplied by the pressure ratio of the turbine operating point.
