Building the motor

[Dominant1]

Do you have a link to the springs you purchased? And why do I need springs?

you need them because your cylinder pressures will be high at 7500 + rpm with boost, you don't want any valves floating:

https://www.livernoismotorsports.com/product/LPP813115-32

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[engineermike]

If you want max power on e85, leave it at 11/1. If you want max power on gasoline and have room for more in the blower&drive, and want max power on 91/93 the the compression is best lowered. I can get much deeper into this discussion but just take a look at the power being made on 93 in the 9.5/1 gt500 vs where coyotes become detonation limited.

On the valve springs I would be careful. Running stock cams and springs you don’t have to worry about any sort of nasty valvespring harmonics because it was all sorted out and tested by the oem. By swapping springs you always run the risk of creating more problems than you fix. More spring pressure isn’t always better. Of course, you have to somewhat balance that with the increased boost and rpm.

On the pistons, have you considered Ross for custom pistons? I bought (and broke) plenty of pistons and were most impressed by custom Ross units.

 

[ReapSow]

[QUOTE="engineermike, post: 2982924, member: 35946"]If you want max power on e85, leave it at 11/1. If you want max power on gasoline and have room for more in the blower&drive, and want max power on 91/93 the the compression is best lowered. I can get much deeper into this discussion but just take a look at the power being made on 93 in the 9.5/1 gt500 vs where coyotes become detonation limited.

On the valve springs I would be careful. Running stock cams and springs you don’t have to worry about any sort of nasty valvespring harmonics because it was all sorted out and tested by the oem. By swapping springs you always run the risk of creating more problems than you fix. More spring pressure isn’t always better. Of course, you have to somewhat balance that with the increased boost and rpm.

On the pistons, have you considered Ross for custom pistons? I bought (and broke) plenty of pistons and were most impressed by custom Ross units.[/QUOTE]

I'm curious as to why your train of thought is such that making max power on a boosted engine is done by keeping a higher compression ratio? It is something I see posted quite often on these forums.

 

[Angrey]

[QUOTE="engineermike, post: 2982924, member: 35946"]If you want max power on e85, leave it at 11/1. If you want max power on gasoline and have room for more in the blower&drive, and want max power on 91/93 the the compression is best lowered. I can get much deeper into this discussion but just take a look at the power being made on 93 in the 9.5/1 gt500 vs where coyotes become detonation limited.

On the valve springs I would be careful. Running stock cams and springs you don’t have to worry about any sort of nasty valvespring harmonics because it was all sorted out and tested by the oem. By swapping springs you always run the risk of creating more problems than you fix. More spring pressure isn’t always better. Of course, you have to somewhat balance that with the increased boost and rpm.

On the pistons, have you considered Ross for custom pistons? I bought (and broke) plenty of pistons and were most impressed by custom Ross units.

I'm curious as to why your train of thought is such that making max power on a boosted engine is done by keeping a higher compression ratio? It is something I see posted quite often on these forums.[/QUOTE]

Compression is the key to maximizing the engine's volumetric output. With 93 or pump gas, there's limits on how much boost you can run safely before you run into detonation (at high compression). Which is why if you want to run lots of boost, with pump gas you lower the compression.

It's a bit of a tradeoff, but obviously more beneficial to run high boost with lowered compression. But optimally, if you want to make even more power you run high boost AND high compression.

This is generally only possible with race fuel or E85 or fuel that has a much better resistance to preignition.

12:1 compression is awesome, but for boosting it, it almost requires E85 or race fuel to go beyond a few lbs of boost. Good news is, it doesn't require that much boost to make decent power (on 93) because it's high compression.

The new GT500 motor is setup to be low compression because they were working with pump gas. It has to spin the blower fairly hard to make high numbers. The 18+ motor and the voodoo don't have to push nearly as much boost to achieve similar outputs.

 

[ReapSow]

I'm curious as to why your train of thought is such that making max power on a boosted engine is done by keeping a higher compression ratio? It is something I see posted quite often on these forums.

Compression is the key to maximizing the engine's volumetric output. With 93 or pump gas, there's limits on how much boost you can run safely before you run into detonation (at high compression). Which is why if you want to run lots of boost, with pump gas you lower the compression.

It's a bit of a tradeoff, but obviously more beneficial to run high boost with lowered compression. But optimally, if you want to make even more power you run high boost AND high compression.

This is generally only possible with race fuel or E85 or fuel that has a much better resistance to preignition.

12:1 compression is awesome, but for boosting it, it almost requires E85 or race fuel to go beyond a few lbs of boost. Good news is, it doesn't require that much boost to make decent power (on 93) because it's high compression.

The new GT500 motor is setup to be low compression because they were working with pump gas. It has to spin the blower fairly hard to make high numbers. The 18+ motor and the voodoo don't have to push nearly as much boost to achieve similar outputs.[/QUOTE]

Thank you for chiming in.

I'm in complete agreement with the red, which is why I'm scratching my head at the blue and trying to decide why running high boost and lower compression isn't the most optimal from not only a tuning aspect but also a fueling one?

I'm not saying eliminate the VE of the engine and run a 7 to 1 with 40 pounds of boost but rather I'm questioning why a reduction from 12 to 1 or 11 to 1 to something like 10 to 1 or 9.5 to 1 and adding more boost wouldn't make life easier while making more power?

 

[engineermike]

I'm curious as to why your train of thought is such that making max power on a boosted engine is done by keeping a higher compression ratio? It is something I see posted quite often on these forums.

Maybe I didn’t explain myself well enough, but I intended to communicate that on pump gasoline (not e85), lowering compression will yield more torque and power before running into a detonation limit.

 

[ReapSow]

Maybe I didn’t explain myself well enough, but I intended to communicate that on pump gasoline (not e85), lowering compression will yield more torque and power before running into a detonation limit.

You explained yourself well and even stated "on e85" I just keyed in on the first part of your post for some reason. My mistake.

 

[Angrey]

Compression is the key to maximizing the engine's volumetric output. With 93 or pump gas, there's limits on how much boost you can run safely before you run into detonation (at high compression). Which is why if you want to run lots of boost, with pump gas you lower the compression.

It's a bit of a tradeoff, but obviously more beneficial to run high boost with lowered compression. But optimally, if you want to make even more power you run high boost AND high compression.

This is generally only possible with race fuel or E85 or fuel that has a much better resistance to preignition.

12:1 compression is awesome, but for boosting it, it almost requires E85 or race fuel to go beyond a few lbs of boost. Good news is, it doesn't require that much boost to make decent power (on 93) because it's high compression.

The new GT500 motor is setup to be low compression because they were working with pump gas. It has to spin the blower fairly hard to make high numbers. The 18+ motor and the voodoo don't have to push nearly as much boost to achieve similar outputs.

Thank you for chiming in.

I'm in complete agreement with the red, which is why I'm scratching my head at the blue and trying to decide why running high boost and lower compression isn't the most optimal from not only a tuning aspect but also a fueling one?

I'm not saying eliminate the VE of the engine and run a 7 to 1 with 40 pounds of boost but rather I'm questioning why a reduction from 12 to 1 or 11 to 1 to something like 10 to 1 or 9.5 to 1 and adding more boost wouldn't make life easier while making more power?[/QUOTE]

There's a lot of factors and in order to pick the appropriate path, everything must be considered (including how much intercooling).

For the guys that run ridiculous boost, you are correct. If I were trying to make 2000 hp, I'd lower the compression and run an assload of boost (with massive amount of intercooling) and a healthy dose of methanol and/or nitrous. You can compress and cool charge air, but there are limited options for calming compression (like methanol or nitrous)

If I were trying to accomplish anything this worldy (like the OP) I'd stay high compression and run E-85 and say 15 psi.

Of course you can run 8.5:1 compression and run 22 lbs and arrive at the similar place, but it requires MORE intercooling and things like belt slip and small pulleys start to come into play.

Basically, the easiest combo is 12:1, low boost and E-85 and more pump/injector.

It can be done on 93, but at much less compression and much more boost and cooling and less pump/injector.

The OP wants to stay pump, so lower compression makes sense.

 

[engineermike]

Thermodynamically and kinematically there are actually power advantages to running lower compression and more boost even if not octane limited. However, these advantages are drastically less than if you are octane limited, plus there are other disadvantages to low compression on a street car. I do think it’s interesting that the 2018 cobra jet runs C16 race gas but they still elected to run only 9.7/1 compression.

 

[Jackson1320]

I'll be building the motor soon. Manley Tuff Rods, custom Weisco pistions, sleeved block ,Clevite Coated H-Series Main Bearings, Clevite H-Series Rod Bearings I already have oil pump gears and crank sprocket and ARP bolts. I'm also going to buy a new oil pump since the motor will be apart, going to purchase a ATI double key harmonic balancer. Keeping my stock heads and cams. Is there anything else I need to replace? Timing chain guides?? Do I really need them? Also what about the main Bearings caps? I want to make 900 to the wheels all day long without issues. Im running a V7JT Vortech blower with id1000 injectors, 18 intake 8 rib set up longtubes with a ben calimer stage 3 transmission with a rxt clutch. Later down the line, I'm going to get a fuel system but for right now... I'll be on pump smh. Dropping the compression to 10:1 . What do you guys think of this build. Is there anything I might need or I'm missing? Thanks for your time

Don’t waste your money sleeving the block at that horsepower, just buy a block support kit Good well into 1200whp. I run/recommend Compstar rods they can handle more horsepower than you’re gonna throw At them cheaper. do not lower your compression actually I recommend Mahle pistons and raise the compression to 11.5 to 1 the Higher compression can make the same horsepower with less boost. Mahle pistons are made of 4032 forged aluminum and it does not expand as much as 2618 aluminum So they don’t rattle on start up and they’re also available in 2618 if thats something important to you but I highly recommend a full skirted piston at that power level. main caps are plenty strong. replace the main timing chains with GT 350 chains. replace the secondary chains With an aftermarket si li, MMR one of them. Stock chain guides are fine. Boss tensioners. Get everything balanced throw in some gapless rings and 900 will be nothing add ported heads, valve springs, valves and This is the exact Engine I have in my car right now

 

[Jackson1320]

Maybe I didn’t explain myself well enough, but I intended to communicate that on pump gasoline (not e85), lowering compression will yield more torque and power before running into a detonation limit.

That may be true but you’re gonna have to run Way more boost. With a centrifugal the cars going to be a dog off the line with low compression. I’m currently running 11.5 to 1 compression pistons and 10lb boost daily and 15lb on water/meth on A centrifugal. With no donation issues

 

[Jackson1320]

To get the benefit from a lower compression you’re gonna need to run 30 pounds of boost. Stay around 11or12 to 1 compression ratio and hit your horsepower goal on 15lbs of boost.
The money you save from not sleeving your block will pay for ported heads. Also with that much horsepower you’re gonna need STDX rod bearings

Everybody’s going to have an opinion on this but how many actually make 900 hp or how many of them have actually built a coyote

 

[engineermike]

To get the benefit from a lower compression you’re gonna need to run 30 pounds of boost...

This is rather exaggerated. Lower your compression to 8/1, run 30 psi, and enjoy 1000+ hp on 93 if that’s your prerogative and you have everything else needed. The Mercedes m139 engine does this and makes over 200 hp/liter. It does it at 9/1 compression and 30 psi on junk gas all day long, so this route has been proven in something more reliable than your typical supercharged mustang.

Or we could be more reasonable and talk about dropping compression from 11/1 to 10/1. Adding 1-1.5 psi boost will recoup anything lost from the compression, but be much safer. Add another 2-3 psi and you’re still safer but making 40-60 more hp on pump gas. IIRC the PBD gt500 (9.5/1) made almost 900 rwhp on 93. Yes, they had to raise the boost to something like 17 psi but 17 psi and 900 rwhp is not possible at 11 or 12/1 on 93 no meth or booster.

 

[robmustang201528]

Since I have to raise the boost... I'm assuming my blower will be working a little harder, which means my blower will get warmer... is this downside of lowering my compression with a blower

 

[80FoxCoupe]

Since I have to raise the boost... I'm assuming my blower will be working a little harder, which means my blower will get warmer... is this downside of lowering my compression with a blower

Dont forget increased parasitic loss

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