What is your current combo or in the works combo?
Highest compression for boost?
- Thread starter trxcobra
- Start date
What is your current combo or in the works combo?
Boss 5.0 iron block, 23 cc (8.5:1) CP pistons, Oliver rods w/ E3.5 alloy bolts, ported intake and heads, factory 04 cams and valves, Pac springs (95 lb seat pressure) and retainers, Cloyes adjustable timing gears, Titan copper head gasket w/SS O-ring, Melling oil pump/Evens water pump, King bearings, ARP "everywhere", Division-X rails, 60 lbs Siemens Deka injectors, BHJ 8 rib double keyway damper, gen II 2.3 Whipple, Accufab TB, Canton road race oil pan and modified windage tray, Ported JBA shorties, J&S Vampire knock suppression system and extensive cooling mods.
The engine is waiting for clearance hone and balance but that won't happen until I finish the chassis as I don't want an assembled engine lying around. I'll be running 15-16 lbs of boost on 91 pump gas. Should easily make 600 hp but the engine is built to handle much more.
We definitely need to make this happen next summer:beer:
An engine with higher compression will always require less boost to achieve the same power level. That's a fact.
Here's where I think most people are at, and why they go low compression:
I want to make xxxrwhp. I want to use pump gas only (no nitrous, no meth) I'd LIKE to do that with as high a compression as possible, BUT since no one can seem to say whether or not what I want is possible with what compression...I don't want to have to build a motor twice because I went too high a compression to hit my goal.
On a limited budget, low compression + high boost is cheaper.
I want to make xxxrwhp. I want to use pump gas only (no nitrous, no meth) I'd LIKE to do that with as high a compression as possible, BUT since no one can seem to say whether or not what I want is possible with what compression...I don't want to have to build a motor twice because I went too high a compression to hit my goal.
On a limited budget, low compression + high boost is cheaper.
Reading back through this I have some suggestion for you. I spoke with L&M about my build a few weeks ago and he said the melling pump wasn't worth the money. He recommended the TSS billet gears in the oem housing instead. Same price, better parts. Next, the double keyed snout. Unless you are running a billet crank, this is a no no as it actually weakens the stock snout. A better option would the 9/16" stud mod. This will retain all of the snouts strength and give you the extra clamping force you need. Instead of the PAC springs, go with the Brain Tooley .525" lift springs; .525" Lift ovate wire beehive springs, 95lbs @ 1.420", 260lbs @ .920". Specs seem familure? They are the identical spring to the manley spring at 1/2 the price. Literally the same spring, from the same spring manufacturer. Skip the cloys adjustable timing gears and go with CLO-S790HP9 (x2), TFS-51800505, CLO-P9139 (x2). It'll save you $150 if you're talking about the gears only and not the whole timing set and get you within half a degree. Hope something out of the was helpful. You'll need the help when we run 'um :beer:
Interesting points
I don't think you can attribute oil pump failures to the gear rotors themselves. Billet steel is pretty tough material and less brittle then the PM factory gears. They just won't break on their own. I think harmonics, movement of the crank snout or ingesting debris can be attributed to the vast majority if oil pump failures. The gears straddling the snout carries some risk. Haven't decided whether or not to cut the second keyway, once I turn my attention to building the engine those details will be decided.
I bet those are the same valve springs I have. When I comes to springs it hard to tell who made them? what they are made of? what heat treatment did they get? They all look the same and you just never know unless you buy directly from the guys who made them. I discussed this topic over with many people with many "opinions". Pac is the largest manufacturer of automotive valve springs and I have a friend who has an inside contact in the engineering dept who had some interesting information on the industry as it relates to our cars (remember the outbreak of Comp spring failure). Their retainers were at 7.5 grams vs. the OEM 9.2 for grins
I only needed the adjustable gear set. I like the acentric adjuster and just bristle at the thought of the slotted hole type which is why I went with Cloyes.
Building engines is the coolest hobby :coolman:
Without race gas it's "fatal" lol
Steve your car runs in the 9s at like 12 psi right.
L&M said the TSS gears in the oem housing were dimensionally superior and an over all better quality of production and finish. Not that one was stronger than another, just better quality. The springs are the same as manley, made on the same line by the same manufacturer and verified by NASVT. I agree that PAC makes great springs, and they were my first choice before I found the Tooley springs. The savings of using oem retainers was the defining factor. My GT supercar lash adjusters and followers cut 7 times that weight per valve anyways. The increase in oil pressure is just a plus.
Having talked to many engine builders I have learned that no two opinions are alike. It can range from: Insightful To: down right bizzar. I have heard nothing but good things about L&M engines but be assured raise this topic in a room full of their peers will result in anything but a consensus. From a fit & finish perspective I found nothing wrong with the Melling pump. I was actually impressed with the precision of the gear rotor and housing assembly.
Being a mechanical engineer I spec precision parts all the time and very little gets past my scrutiny unless it's something I can see like the alloy or heat treatment. Things like this:
Your looking at where the entire output of the oil pump gets squeezed thru so I did this:
Every restriction you remove results in more volume and pressure down stream with the cams are last in line for lubrication.
I think we are getting a bit off topic here. This is a good thread which I'm sure many of the "listeners" are getting a good perspective on this subject and its a good debate.
We are getting off topic. However I would like to briefly visit this subject one more time and get some opinions. I think we pretty much beat the original thread topic to death anyways.
TSS
Melling
Stock pump specs:
Pump to cover .002
Tip to tip .004
pump to body .005
TSS gears in stock new oil pump housing:
Pump to cover .003-.004
Tip to tip .005
pump to body .002
Melling Pump Specs:
Pump to cover .002
Tip to Tip .004
Pump to body .010
TSS
Melling
Stock pump specs:
Pump to cover .002
Tip to tip .004
pump to body .005
TSS gears in stock new oil pump housing:
Pump to cover .003-.004
Tip to tip .005
pump to body .002
Melling Pump Specs:
Pump to cover .002
Tip to Tip .004
Pump to body .010
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Is the TSS pump in that pic new? There is no sign it has ever been used not even a scuff mark. That Melling pump is ugly. Was that the source of the failure or a symptom of it? It looks like the gear rotors were forced into one another by the transverse marks across the teeth which suggest crank snout flex. One guy forgot to install the thrust faces on his crank bearings making the pump the thrust bearing, a mistake he'll never repeat :nonono:
Lethal Performance built a pretty wild Trinity 5.8 with 10.5:1 compression and a Whipple 4.0 pullied to nearly 25PSI. Running on E-85, this motor made 1126 HP at the wheels.
There's a great in-depth article about this build in the latest issue of 5.0 Mustang Magazine, but I found a cool teaser video:
[youtube_browser]_kBjGijogHc[/youtube_browser]
There's a great in-depth article about this build in the latest issue of 5.0 Mustang Magazine, but I found a cool teaser video:
[youtube_browser]_kBjGijogHc[/youtube_browser]
E-85 is ~100 octane. I think we all understand what's capable with either E-85 or race gas.
Melling
Just an "FYI", I'm pretty sure the MMR pump is a rebranded Melling.
BTW, good showing at MIR.:rockon:
E85 is actually around 105 octane. But that wasn't my point. My point was that they chose to build a higher compression motor than stock rather than lowering the compression. Why? They knew even with a massive 4.0 whipple that they'd be pushing it to its limits, so they'd be able to make more power without having to spin the blower faster than its efficient operating range.
There's actually a quote from the magazine article of you haven't had a chance to read it yet: "...The biggest factor with this car is the compression..." - "For the '13 [GT500 engine], we built a high compression motor knowing it would make more power with less boost."
Take a stock '13 GT500 for example: in addition to the bump in displacement, this motor has higher compression (9.5:1) and more boost (15 PSI, using a more efficient blower) compared to earlier models.
With a lower compression motor, you'd need more boost to make as much power. What happens when you run more boost? There are higher parasitic losses and higher IAT's, especially when nearing the design limits of a given blower. Lets say you wanted to make an additional 30 RWHP and you had the choice of higher compression or more boost. If you were to run lower compression and higher boost, your motor would need to make an additional amount of power to spin the blower to make the extra boost necessary for 30 more WHP. The higher compression motor doesn't have to work as hard to make the same amount of power at the wheels because of not only the power advantage but also the lower parasitic losses.
With newer engine technologies and better tuning techniques it's possible to run higher compression in boosted applications than ever before. You can change the ignition timing. You can change the type of fuel you run. You can add meth injection (with a timing retard failsafe). You can get a more efficient power adder designed for higher boost that has lower parasitic losses and lower IAT's All of these things are better at managing detonation than going with a lower compression ratio because they can all be changed and tweaked to work as a combination. Compression ratios are set in stone once the motor is built. So I'd rather go more aggressive with the compression and manage detonation with said variables.
Just wait until direct injection becomes available in mustang V8 engines. It's coming... The coyote cylinder head already has a boss cast in the combustion chamber where a DI fuel injector would normally be located. It's already designed for it. With DI, it will give tuners even more precise control over fueling to help control detonation, allowing even more compression and more boost.
Take the ecoboost motors for example. They all have a 10:1 compression ratio. The twin turbo v6 makes 12PSI in FWD trim and 14PSI in the F150. The 1.6L 4cyl makes 16PSI and the little 1.0L 3 cylinder will make as much as 20 pounds of boost--- STOCK! That's wild.
There is no single answer about the highest compression with boost. It depends on pretty much every variable that exists in a gasoline engine, not to mention the extra variables associated with forced induction.
But the trend with new engine designs, more sophisticated tuning, and easier access to fuels such as e-85, it's becoming less necessary to sacrifice compression as a means of managing detonation to run big boost.
I don't doubt that people will push the limits even further with the next generation of mustangs using direct injection and more sophisticated tuning in addition to proven techniques such as e-85, meth, and more efficient power adders to be able to run even higher compression ratios upwards of 12:1 or hopefully higher than that.
Would the mustang aftermarket be as vibrant as it is today if everyone thought conventional wisdom and perceived limitations couldn't be overcome? HELL NO!
I don't think anyone is doubting any of the points your reiterated in this post. What people are concerned about is hitting their power goals on pump gas only, and NO one wants to risk saying "oh yea, that's doable at 10:1." All you'll get from people on this forum is snide comments about how folks will "never understand." And the occasional "well I did it with completely massive cams and 42:1 compression."
Well I don't know about you, but I'm not going to drop $7k on a built high compression motor only to find out that it pings 100hp below my power goal. Going low compression and cranking up the boost is the safe bet for the wallet.
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