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CT4-V Does anyone want to work on the LF4?

Cadillac CT4-V model

BKC1

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The LF4 is an interesting engine. It's capable of making over 750 RWHP, but the reliability up there is questionable. If you want this engine to be taken seriously, it needs to be able to make 750 RWHP all day without hitting coolant temperatures of 270F+. It also needs to be able to make 1000+ RWHP over short stints reliably.

Over the last 3 years, I've been reaching out to numerous companies--all the ones that make parts for the ATS-V and CT4-V BW, plus some you've probably not heard of--and nobody is developing foundational performance parts for these engines. I'm talking head gaskets, main bearings, rod bearings, billet main caps, main cap studs, connecting rod bolts, etc. We need things like that, plus ported intake manifolds that can support larger throttle bodies and/or entirely new intake manifold castings for larger intercoolers. We need people to get involved and help raise the demand signal for oil cooler adapters, and people to trailblaze getting full size "race" PWR heat exchanger into the engine bay. Finally we need people to knock down DSC Sport's door and get them to develop a V4 magnetic ride controller and a tuning profile (remember, each car needs to be tuned on the track and the street) and figure out the differences between the mag ride shocks.

Not sure who's out there on this forum, but if there's interest in working (not uselessly commenting ) on new parts and adapting existing part to the LF4 let me know. This is where I think we currently stand:
  • 5-layer MLS head gaskets are available but need to be tested (I've got a set on order)
  • One vendor is making billet steel main caps instead of aluminum ones, which is not a good idea--we need billet aluminum main caps with splays
  • Multiple King bearings are available, but nobody wants to put in the effort with ARP bolts to figure out the proper amount of squish
  • The connecting rod bolts apparently have an ARP equivalent in the Audi V8 4.2L (i.e. ARP 204-6304, offered in a set of 16 only) but I'm dubious they fit; the one guy that knows the part numbers won't share them.
  • There are GM HF V6 torque plates available (Gen I) (Gen II), but they're the wrong thickness to emulate the LF4 head--regardless, nobody has put in the investment to determine if they fit and run them with ARP 625+ studs to figure out how distorted the bores get and what the best piston/ring configuration is after hot honing
  • For a while, one of the throttle body companies was going to offer an intake manifold porting service to support a 72mm or 80mm LGX/LGZ throttle body but decided it was too hard; I'm currently working on a DIYer jig that people can use to port their own
  • Since nobody understands this better than me, I'm forging ahead with the improved wastegate project and will report back with dyno results showing spool times between gear changes.
  • Once my finances rebuild, I'll pull the trigger on the custom flywheels to support installing a LT4 Tilton ST-246 in the LF4; should reduce clutch rotating inertia by 51% and drop 18 lbs off the car, approximately.
Off the beaten track, unrelated to the LF4:
  • I'm finishing up testing the 3D printed NVH isolators and DIY aluminum coilover sleeves for use with Swift linear springs and rate testing the ATS-V/CT4-V BW springs and sway bars with my own welded rig and strain gauges; my objective is to have a kit out this summer that permits another 20mm of front wheel inboard and 1" of height adjustment at the same exact suspension rates as OEM. I don't have CT4-V BW front shocks to test fitment on, so if anyone has a set that they can measure please reach out. I'm also willing to buy a set, after I finish testing the CT4-V BW rear shocks on my ATS-V.
  • For the ATS-V specifically, I have a CTS-V3 fuel tank in stock and will be doing analysis and fitment tests to figure out how to get 19 gallon fuel capacity. Both the CT4-V BW and CT5-V BW have a 17 gallon tank so I don't think the same effort can be extended to the 4th gen platform.
  • For the ATS-V M6 specifically, I have a working remote start system that I'm finishing testing (trying to get the OEM remote to start the car instead of having a secondary one, which halves the prices for the mod)
  • I'd really like to see proper skirts made that extend the sides down (not out), similar to the Nowicki design for the CTS-V3, ground effect extensions for the rear (especially on the ATS-V), and a flat floor extension out the back that covers the hole left when you remove the OEM exhaust.
  • Way down the priority list is a set of DIY laser-cut plates that would allow you to install and remove a 1500 lb Curt trailer hitch in 5 minutes for one of those very small trailers for track days (e.g. just enough to fit 4 wheels and associated gear).
  • I want to work with Revshift or Creative Steel on designing a height adjustable upper shifter stalk piece with better NVH isolation than the Hurst shifter and polyurethane transmission cross-brace bushings. Based on my experience with older V-series cars, rubber bushings sag over time, resulting in various problems.
  • I have a ton of reduced-head wrench size titanium and ARP stainless bolt recommendations to get rid of all the stuff on the car that's either prone to rust or hard to wrench on. This kind of stuff is like "the last 1%" and not many people find it interesting, so I haven't shared it. If you're interested let me know.
I want to see if we can push the engine RPM up from 6500 to 7200 RPM. I keep hearing "just add more turbo" and seeing people pooh-poohing the idea that the stock system is restrictive despite the math saying the OEM system is overwhelmed at double the LF4's stock horsepower. I'm not necessarily against adding more turbo but not until we get the intake temperatures down, the oil temperatures down, the cylinder wall straightness issues resolved, and reliability up.

The problem with adding more turbo is, it comes at a cost both literally and in terms of lag, I see very little actual, numerical evidence that anyone has tested this theory and proven that more turbo is necessary. One byproduct of a very inefficient system is heat; better to not have heat at all then spend tons of money and time removing it. It's easy to do 1/8 mile and 1/4 mile runs and say "see more turbo works" but what you don't see is those guys posting their datalogs showing temperatures or running sustained track events.

What we see from track events is that, at 650-725 RWHP, the oil temperature is rapidly getting to 270-300F which has resulted in total LF4 failures. We also see excessive blowby and oil contamination leading to bearing failure, some of which is unavoidable but (I think) partially due to poor cylinder wall straightness. So based on all of this, my recommendation is to strengthen and improve the foundation before we decide where to go next.
 
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For anyone wondering what I'm talking about WRT billet aluminum main caps with splays:


If you don't know who Steve Morris is, this video ain't for you.
 
Definitely interested in 'copying' builds to get to where I want. Meaning buying the parts that are made and tested and proven.
 
To your point on excessive blow-by during track events: would a catch can be a worthwhile "peace of mind" addition to an otherwise stock (for now) 4VBW that will see multiple track events per year?
 
The LF4 is an interesting engine. It's capable of making over 750 RWHP, but the reliability up there is questionable. If you want this engine to be taken seriously, it needs to be able to make 750 RWHP all day without hitting coolant temperatures of 270F+. It also needs to be able to make 1000+ RWHP over short stints reliably.

Over the last 3 years, I've been reaching out to numerous companies--all the ones that make parts for the ATS-V and CT4-V BW, plus some you've probably not heard of--and nobody is developing foundational performance parts for these engines. I'm talking head gaskets, main bearings, rod bearings, billet main caps, main cap studs, connecting rod bolts, etc. We need things like that, plus ported intake manifolds that can support larger throttle bodies and/or entirely new intake manifold castings for larger intercoolers. We need people to get involved and help raise the demand signal for oil cooler adapters, and people to trailblaze getting full size "race" PWR heat exchanger into the engine bay. Finally we need people to knock down DSC Sport's door and get them to develop a V4 magnetic ride controller and a tuning profile (remember, each car needs to be tuned on the track and the street) and figure out the differences between the mag ride shocks.

Not sure who's out there on this forum, but if there's interest in working (not uselessly commenting ) on new parts and adapting existing part to the LF4 let me know. This is where I think we currently stand:
  • 5-layer MLS head gaskets are available but need to be tested (I've got a set on order)
  • One vendor is making billet steel main caps instead of aluminum ones, which is not a good idea--we need billet aluminum main caps with splays
  • Multiple King bearings are available, but nobody wants to put in the effort with ARP bolts to figure out the proper amount of squish
  • The connecting rod bolts apparently have an ARP equivalent in the Audi V8 4.2L (i.e. ARP 204-6304, offered in a set of 16 only) but I'm dubious they fit; the one guy that knows the part numbers won't share them.
  • There are GM HF V6 torque plates available (Gen I) (Gen II), but they're the wrong thickness to emulate the LF4 head--regardless, nobody has put in the investment to determine if they fit and run them with ARP 625+ studs to figure out how distorted the bores get and what the best piston/ring configuration is after hot honing
  • For a while, one of the throttle body companies was going to offer an intake manifold porting service to support a 72mm or 80mm LGX/LGZ throttle body but decided it was too hard; I'm currently working on a DIYer jig that people can use to port their own
  • Since nobody understands this better than me, I'm forging ahead with the improved wastegate project and will report back with dyno results showing spool times between gear changes.
  • Once my finances rebuild, I'll pull the trigger on the custom flywheels to support installing a LT4 Tilton ST-246 in the LF4; should reduce clutch rotating inertia by 51% and drop 18 lbs off the car, approximately.
Off the beaten track, unrelated to the LF4:
  • I'm finishing up testing the 3D printed NVH isolators and DIY aluminum coilover sleeves for use with Swift linear springs and rate testing the ATS-V/CT4-V BW springs and sway bars with my own welded rig and strain gauges; my objective is to have a kit out this summer that permits another 20mm of front wheel inboard and 1" of height adjustment at the same exact suspension rates as OEM. I don't have CT4-V BW front shocks to test fitment on, so if anyone has a set that they can measure please reach out. I'm also willing to buy a set, after I finish testing the CT4-V BW rear shocks on my ATS-V.
  • For the ATS-V specifically, I have a CTS-V3 fuel tank in stock and will be doing analysis and fitment tests to figure out how to get 19 gallon fuel capacity. Both the CT4-V BW and CT5-V BW have a 17 gallon tank so I don't think the same effort can be extended to the 4th gen platform.
  • For the ATS-V M6 specifically, I have a working remote start system that I'm finishing testing (trying to get the OEM remote to start the car instead of having a secondary one, which halves the prices for the mod)
  • I'd really like to see proper skirts made that extend the sides down (not out), similar to the Nowicki design for the CTS-V3, ground effect extensions for the rear (especially on the ATS-V), and a flat floor extension out the back that covers the hole left when you remove the OEM exhaust.
  • Way down the priority list is a set of DIY laser-cut plates that would allow you to install and remove a 1500 lb Curt trailer hitch in 5 minutes for one of those very small trailers for track days (e.g. just enough to fit 4 wheels and associated gear).
  • I want to work with Revshift or Creative Steel on designing a height adjustable upper shifter stalk piece with better NVH isolation than the Hurst shifter and polyurethane transmission cross-brace bushings. Based on my experience with older V-series cars, rubber bushings sag over time, resulting in various problems.
  • I have a ton of reduced-head wrench size titanium and ARP stainless bolt recommendations to get rid of all the stuff on the car that's either prone to rust or hard to wrench on. This kind of stuff is like "the last 1%" and not many people find it interesting, so I haven't shared it. If you're interested let me know.
I want to see if we can push the engine RPM up from 6500 to 7200 RPM. I keep hearing "just add more turbo" and seeing people pooh-poohing the idea that the stock system is restrictive despite the math saying the OEM system is overwhelmed at double the LF4's stock horsepower. I'm not necessarily against adding more turbo but not until we get the intake temperatures down, the oil temperatures down, the cylinder wall straightness issues resolved, and reliability up.

The problem with adding more turbo is, it comes at a cost both literally and in terms of lag, I see very little actual, numerical evidence that anyone has tested this theory and proven that more turbo is necessary. One byproduct of a very inefficient system is heat; better to not have heat at all then spend tons of money and time removing it. It's easy to do 1/8 mile and 1/4 mile runs and say "see more turbo works" but what you don't see is those guys posting their datalogs showing temperatures or running sustained track events.

What we see from track events is that, at 650-725 RWHP, the oil temperature is rapidly getting to 270-300F which has resulted in total LF4 failures. We also see excessive blowby and oil contamination leading to bearing failure, some of which is unavoidable but (I think) partially due to poor cylinder wall straightness. So based on all of this, my recommendation is to strengthen and improve the foundation before we decide where to go next.
Honestly a 7200 rpm redline at stock ish power would be everything I want in this car lol. Power seems perfect for the handling prowess. Maybe a touch more to say 500 wheel horsepower…

I’ll be keeping a close eye to see if that becomes a reality. Anyone know if the engine is well enough balanced to do 7200 reliably as is? I thought some lfx variants did go to 7200. Thanks for all the research you’re putting in!
 
Honestly a 7200 rpm redline at stock ish power would be everything I want in this car lol. Power seems perfect for the handling prowess. Maybe a touch more to say 500 wheel horsepower…

I’ll be keeping a close eye to see if that becomes a reality. Anyone know if the engine is well enough balanced to do 7200 reliably as is? I thought some lfx variants did go to 7200. Thanks for all the research you’re putting in!
If you add stronger valvesprings and a Super Damper, this is not a problem. Tapout Tuning stocks both products.
 
If you add stronger valvesprings and a Super Damper, this is not a problem. Tapout Tuning stocks both products.
When you tune an LF4, do you increase the redline? I haven't seen a dyno sheet that goes above 6800 RPM, even on the highest horsepower builds.

ATI Superdampers are tuned for a specific frequency range. Do you know what ATI Racing did to develop the LF4 Superdamper (e.g. did they measure actual LF4 crankshaft harmonics or extrapolate from a different engine)?

I'm sure ATI wouldn't offer up this info, but I'll ask anyway: did they do anything special like bias the damper toward the high frequency side of things to account for lightweight forged pistons, which pushes up natural frequency?

-------------------

Adding an ATI Superdamper and stronger valvesprings will reduce harmonics and increase valvetrain stability. The reduction in harmonics will reduce the stresses on the crankshaft that lead to crank failures. The increased valve stability will help maintain a linear powerband. Those are solid improvements, but it's not nearly enough.

What I want to know is what GM balances the rotating assembly to (which is what DesertRJ was asking about), OEM bearing clearances, block stiffness, rod stiffness, and the limits of the main cap and rod bolts. Just to name a few things.

We don't know all the failure modes of the LF4 yet. We know several, because they've been documented, but there are a bunch of questions yet unanswered. For instance, if you increase power to 600 RWHP, the oil cooling system is inadequate, and you will spin a rod bearing unless you keep the oil temps below 250F, which is impossible on a circuit track. At 725 RWHP+ there's evidence that the crank is walking all over the place, which could be a function of several things.

If I were to draw a line for easy reliability, I'd say it's around 3 HP per cubic inch, which is 525 RWHP. At 3.5 HP per cube, 615 RWHP, you're above limit of the as-built engine. To contextualize this, 3.5 HP on a 6.2L LT4 is equivalent to 1119 RWHP. How many LT4/LT5 builds do you know of that can handle that long term? On the stock block, there are zero.


I want you to look at the mod list in this video--particularly the LME LTR 427 sleeved aluminum billet block. There's a typo in the description but that is either the 1500HP LTR or 1800HP LTR build, which costs $32k or $37k. That billet, max-parts, max-effort engine is putting out 1319 RWHP on 427 CID for an estimated 3.63 HP per cubic inch. So when we talk about making 4 HP per cubic inch on a stock block, we need to get very serious about the engine build and in confronting unrealistic expectations regarding reliability and cost.

The secret that most of these guys running big numbers don't want to tell you is that most of them have been through 2 or 3 blocks already; sometimes only getting five, ten, or twenty thousand miles out of a LF4 between failures. If that was more widely known, it would put an end to most big dollar LF4 builds, which is not what anyone wants.

I put out RFQs to four machine shops on the east side requesting a price to take my LF4 apart and document everything. If there are issues with the rotating assembly balance or block, I will let everyone know. After we measure, we're going to remeasure with ARP fasteners and some other stuff (e.g. torque plates) and see what moves. This is going to be a expensive project and I'm not asking for money--I want other people to step up.

There are four projects I don't have time to get into yet, two of which cost money, and the other two are free (costs time). If someone wants to take a crack at these it would be helpful.
  1. Build an aftermarket oil cooler kit using the thermostatic Improved Racing ENV-135 sandwich plate as a starting point and a Setrab ProLine oil cooler. Nobody knows if the sandwich plate fits, so it's a $300 financial risk you'd be taking, plus whatever else for a bunch of Send Cut Send brackets and hoses. I've already spoken to Jerry @ IR about the dimensions as well as building an OEM oil cooler adapter, similar to the LT4 model. He and I did enough to confirm that the sandwich plate will thread in on both sides, but we don't know if there's enough room around that area to get the job done.
  2. Do some dyno pulls with fresh cheap plugs, cut them, and read them (see video link below). Let's start getting some flow balance data on the stock manifold so that we can start setting per-cylinder fuel trims.
  3. The OEM pump in our cars is a standard pressure, standard volume Melling M353, which is an improvement over the older LFX and LY7 pumps. Many people sell the M353 as a "high volume" upgrade for older cars. However there is no high volume version of this pump. I sent Melling an email requesting a high volume version with no response. Do me a favor and make a bunch of noise at Melling asking for a M353HV.
  4. Estimate the increase in connecting rod bolt stress at 6600, 7200, and 7800 RPM. There are a bunch of books on Amazon and journal papers that give you ways to do this. I'm not saying do an FEA or precisely determine the stress, I'm saying estimate the increase so that we assume the OEM rod bolts have a safety factor of X, we can say what RPM is safe and unsafe without upgrading.
Getting high volume out of the pump is critical to keeping the rod bearings lubricated at high RPM, avoid losing the wedge, and prevent spinning a bearing. The oil also needs to be cool enough to keep the journals cool and prevent bearing delamination. People forget that the oil is cooling the bearings and the bearings are running tens of degrees above the oil temperature (+50-100F). There is no such thing as too high volume, especially when you're running high RPMs, where the oil is getting extracted from the rod journals by extremely high forces.

Engine Bearing Temperature.gif


Videos:




 
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I'm following this, it's great analysis!

This platform is phenomenal, I'm hoping being a smaller engine than the big brother 5BW we can get this to rev out a little higher than the Lt4 which is almost double the displacement and 2 cylinders more.

I know on the LS3 a simple tune could bump the redline up about 500 safely.
 
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This platform is phenomenal, I'm hoping being a smaller engine than the big brother 5BW we can get this to rev out a little higher than the Lt4 which is almost double the displacement and 2 cylinders more.

I know on the LS3 a simple tune could bump the redline up about 500 safely.
We agree this platform is phenomenal and we take these engines past 7,000 all day long with stronger valve springs.

 
Thank you to all the vendors and innovators working to produce solutions for more reliability at stock and elevated power levels.

Without an aftermarket oil cooler to maintain oil temps under ~220 F, no amount of “foundational ” work will offset oil that’s sheared and is barely thicker than 0W16 oil.if you run E, please recognize that DI and an E-blend require very frequent oil changes.

I’d like to see a supplemental port induction system developed for the LF4 for both power and the ability to keep the valves clean. Harrop( Australia in conjunction with US HQ based in Dayton, Ohio) has developed and released port plates with shorty LSA style injectors that sit inside the LT4 valley plate. Think outside the box!
 
Thank you to all the vendors and innovators working to produce solutions for more reliability at stock and elevated power levels.

Without an aftermarket oil cooler to maintain oil temps under ~220 F, no amount of “foundational ” work will offset oil that’s sheared and is barely thicker than 0W16 oil.if you run E, please recognize that DI and an E-blend require very frequent oil changes.

I’d like to see a supplemental port induction system developed for the LF4 for both power and the ability to keep the valves clean. Harrop( Australia in conjunction with US HQ based in Dayton, Ohio) has developed and released port plates with shorty LSA style injectors that sit inside the LT4 valley plate. Think outside the box!
port injection* and it's not thinking outside the box, it's relatively common across many platforms. PI comes with its own set of pros and cons. You have to worry about additional fuel lines, additional injectors, wiring in the PI controller, getting it tuned, and it's another point of failure. Personally I like sticking with just DI unless it's an OEM dual injection setup like Toyota D4-S, Gen 3+ Coyotes, and B58tu2.
 
Sir, be polite.

I am well aware of supplemental port and/or OE dual systems but “outside the box” refers to placement of the port injector on a DI application. Part is physical packaging and the remainder is fluid dynamics.

I appreciate your work on the platform but fuel must be addressed sooner or later. Methanol has its place but in the wrong hands is less reliable than a “Flying Toilet”.
 
There is lots and lots of geek going on here.

I, for one, like it.

I did the same for other stuff. Recently worked on rear subframe lockout kit development as chassis dynamics are what keep me up at night, strangely.

If anyone is intersted in seeing what I've done, check out www.revelryracing.com.

So far, no ATS-V folks have complained of the sway that the V3 and Camaro guys get, so I hadn't approached it (only the V3 and CTS V-Sport with LF3). But, if there's enough interest, I would. In fact, I think I have 80% of the kit that is already applicable, so . . . lemeno.
 

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