Intended for the performance experts.

Which produces more power on same engine with identical blower?

11:1 Compression with 5 pounds boost, or 9.5:1 Compression with 14 pounds boost. Pros and cons?

Curious minds need to know. Thanks, Robert

 

I'm just going to play with estimates here but maybe it'll help.

Isn't it something like 10hp for every half point of compression? We'll go with that.

400hp 11:1cr
370hp 9.5:1cr

400hp + 5psi = 530+/- hp
370hp + 14psi = 720+/-hp

These numbers are taking out a lot of variables that will effect the final outcome a great deal but you can see somewhat of the difference at least. By tripling the boost on an engine making close to the same original hp, there should be a great deal of power increase. However, you have to keep in mind the blower's efficiency range and the timing and cylinder pressure. There is a lot more heat generated by that much boost. It's not as simple as X cr/psi vs Y cr/psi. Many factors come into play and it's the efficiency of the entire build that will determine the most power and reliability. I'm sure someone else can explain it better or perhaps the shop doing the build/tune.

 

That was precisely the concept explanation I was seeking! Thank you so much.

I told my elementary school teacher once that I am not as dumb as I look, but she responded immediately: don't worry, you could never be that dumb.

Robert

 

You dont need to lower compression to 9.5:1 to run 14psi.

Powerlabs is at 15 with 10.5:1 at sea level.

I ran 10.9:1 (stock) with 15psi with no issues.

MrBig ran 17psi at 10.4:1 for 35k miles.

Why some drop compression like that makes no sense in the world of meth injection. I'd convert to E85 long before I'd do that.

 

SPin, how much boost you think a 9:1 engine could run? THat is what my LSX376 has.. Need to get a F1-r on it.. Hoping it will be out of the shop Friday..

 

Why run meth if you dont have to. IMO its better to play it safe and not worry than deal with issues. Why take chances if you dont have to. What is there to gain vs what is there to lose. If your building it from scratch you have the option to build it right.


trenaman tuning is the key

 

cool, I am not running meth on my build, I am running 109octane though..

 

That is a pretty open ended question. I would think 18lbs on pump fuel depending on restrictions. (like every single part that goes into your 9:1 engine) It can certainly make alot of power.

 

I had an 8.5:1 SRT4 turbo that ran 27#'s flash boost and 23#'s steady with stock internals on 100 Octane. 2.4L and 270 FWHP.

 

I run 16.8:1 and 32lbs of boost. oops thats my 1 ton.



Couldn't help myself.

 

Meth lowers IATs which all FI builds benefit from even if you dont tune for more power with it. You gain 30rwhp even if you dont tune for it. Taking chances is banking on pump gas. You are one bad tank of gas away from a new engine. Meth is playing it safe. If you dont tune for more power, (meth will get most people 50-70rwhp if you tune for it) and leave the tune as is but add meth injection, you are adding the equivalent of 115 octane. If the meth fails, youre in the same boat you were in without but you lose the power gained from lower IATs. Its detonation protection across the board. The only danger that would support your position is if the car was tuned for the use of meth and it fails. How is this any more dangerous than retarded voltage booster people use instead of a real fuel system? A fuel injector can get clogged or a fuel pump burn out and both of these situations is helped with meth. I've installed a lot of meth kits and never hear of them failing. Periodic testing of the system builds in the safety. How often do people check octane in thier gas?

Not running meth is idiotic and most shops wont boost you over 600rwhp without it. ECS wont.

 

When you go with a reputable shop for your build, you go with the parameteres your mechanic choses. When you see reputable shops building 800rwhp cars at 9.8:1, it shows it works.

As I said before Mr BIG never blew up and was at 760 to 800rwhp on 10.4:1 compression for 35,000 miles. He was at 15-17psi the whole time. Meth rocks. I believe he was at the Tex mile and it failed to fire but the safe tune Taylor from DP had in it wasnt tuned on the ragged edge for meth's octane and detonation suppression power gains.

Water and meth injection for detonation suppression is implemented widely in professional drag racing and I'd like to think these guys know what theyre doing. Running on pump gas alone isnt smart.

 

LOL, I'm well aware of what meth does.
I don't care what some other people do to be honest. We build for longevity and safety and our own standards. Check HKE's reputation ... none finer in the business for a reason. Some people run 12:1 (n/a) on regular pump gas but we don't. I don't think compression is a bragging right but its gets treated like it for some reason. Its freaking FI, there is no need to push the compression.
Yes your right and those cars run 1/4 mile at a time, don't sit and heat soak in traffic and don't get exposed to crappy gas. We look at it like this.. can I jump in the car and drive cross country without issue.... building it a little safer doesn't hurt a thing. Call it conservative if you want. We will build what ever the customer wants but we advise as if it were our own.

direct from the man himself and some of the fastest trucks and cars on the planet run his engines. No one says it cant be done, we like to error on the side of caution. You wont see one single shop post up.. hey we blew the heads right off this car on the dyno the other day ( slight exaggeration) but it happens... as well as bearings spinning on new engines on their first dyno run. You don't see the failures posted up because no one wants to be associated with it but it goes on. We approach it as if it were the last engine I can afford to stick in my car. I want it to be perfect and last for ever. SO if we error on the side of caution we know we're not going to waste anyones money. Call me crazy if you want...LOL

 

Thank you all for your thoughts and ideas on the original post question. It may be apparent to most, but may be worthy to state the obvious: The original question concerns the Z06 and particularly the 427 with its stock (static) 11:1 compression.

One element of the original post that I should have clarified is that the Supercharger considered for the question was very capable of effectively supplying up to 20 pounds of boost, or more.

I believe I have learned that with higher initial static engine compression of 11:1, combined with induced boost of merely 5 pounds, or slightly higher, will apparently produce ample (safe and dependable) H.P. efficiency.

True, there are many other variables. Yes, one could introduce 14 pounds of boost on 11:1 static engine compression, but then the potential of subjecting all the other prime engine components to mechanical stress failure increases.

To acknowledge other worthy points of view, perhaps at great expense, one could replace all other prime components with far more strengthened ones, and could thus use high initial static engine compression with higher than 5 pounds boost resulting in enormous H.P. gains. It appears, however, that such large additional expense for stronger components may only lessen, but not eliminate, possible engine component failures due to very high EFFECTIVE compression ratios.

You're a great group and I have both enjoyed and learned from your combined wisdom. Hopefully, there will be more opinions added. Thanks, Robert

 

I've heard that higher compression engines are more responsive, as in throttle response and the perceived liveliness of the engine. Since it relates to the same theory, perhaps someone can explain if there is any truth to that? If it is true, would a higher compression lower boost engine be more fun if high HP is not the ultimate goal?

 

LoL

Powerlabs showed what your compression point of view does:

On 11psi he made 597rwhp and 518rwtq at 10.9:1 compression. He got 30k out of it without meth. Then he built a 9.6:1 6 liter and raised boost to 15 psi. The result: He gained only 20rwhp at peak, lost 70rwtq in the midband, and gas mileage went down considerably. this was with the agreesive tune you can run on meth. In other words it took 4psi and lost power.

In response to the low compression BS he raised his compression back to 10.5:1 and then made 688rwhp, restored the lost compression and gas mileage. Low compression slugs are built for tuners that dont want to warranty a true performance build.

If you can state the screen name of someone you built a car for that runs low compression and no meth on high boost and over 650rwhp, please do so. I'd love to talk to that customer.

As for Erik Konig, you keep trying to align yourself with his work and all you are is a reseller of his shortblocks. He is in Texas far from where you are. There is no 'we' on the part of you and HKE. The VAST majority of his shortblocks are built for customers who do thier own installs such as Dallas Performance who installs his shortblocks and yes, DP runs meth. Thats the same Dallas Performance who ran 10.4:1 at 15+psi on Mr Big's build that at 35k got a new HKE shortblock to replace the still working stock one. So 14psi doesnt need low compression and many, many poeple run that or more boost on a stock compression motor.

I, like 99% of all tuners, run meth. (yes I have a shop on Academy Blvd in colorado Springs where I do real installs some as high on 42psi boost) You would be hard pressed to find any real tuner that does installs that agrees with your meth view. I post to shed that light for others who read what you're saying and dont know if they should run meth. Meth has saved a lot of motors.

On the topic of N/A motors, dynamic compression falls with huge cams so using 12:1 on pump gas is 100% correct if the dynamic compression supports it. On N/A motors it has been demonstrated to also benefit from using meth and other tuners besides myself do just that such as RPM in California. Cartek who pretty much owns most of the H/C records runs high 11's in compression and I havent heard of them blowing up from it.

 

You have no clue what our arrangement is what so ever. He and I got together and decided what I was going to offer, how they were going to be built and how it would be approached. This was not some 5 minute deal either it was planned over the course of 3 months. In that time we talked about theory and application and not building shotty engines on the ragged edge. He decided how and what and to be honest my engines were of a better cut to begin with. Only Callies Compstar and above. But we've relaxd on that a bit for the more budget minded people.

HKE builds short blocks, long blocks + and when they do the complete build the cars usually runs faster than when some other shop gets a short and puts heads on.
3300 lb car at 9.4 second n/a on pump gas... show me who else did that and their wife drives the car to work.
You seriously don't have a clue.

You can run all the compression you want I don't care one single bit. Just because you know a couple vettes doesn't mean a thing to me.
HKE has the fastest truck in the country on his engine and has n/a engines that run 650+ RWHP FYI. ( no meth there sunshine) Racing is far from daily driving.

If you want to advise people to run a million to one and 4000 lbs of boost go right ahead. I don't care one single bit but you aren't going to buy them a new engine are you?
We look at it differently and I echo what I was taught from a master builder and instructor. When you start building engines and instructing at a school to build racing engines then I'll listen to you.

 

Yes more compression makes more power but if high HP is not the goal there is no need for the FI... unless your under cubed.. then you need it.

 

Again, a long list of HKE/Eric Konig's work. I have no doubt his work is one of the best around. I'm not disputing it. Its not your work. After a kazillion years I did get him on the phone finally and you are just a reseller as per him with no tech input.

You keep trying to pass off his work as your's. I dont care what amount of time you spent on the phone with him. Other guys know your story and pass it on behind the scenes.

I've witnessed some of your bashing threads arguing with forum tuners and members in how you're right and everyone else is wrong. The last round with got you banned from LS1tech. You fight with the top tuners who actually build cars that actually get tracked with engines they build and they dont blow up. Yes, LG, Dallas Performance, Cartek, ECS, Virginia speed, RPM, and the list goes on, all like and use meth injection for safety.

Low compression with no meth is the only thing that is right and only HKE builds motors that stay together....OK

As for the N/A cars running faster than 9.4 here is the list of them from LS1tech:
http://www.ls1tech.com/forums/drag-r...s-any-c-i.html

ASHWS6 ran a 9.505 at 143 and I know his motor is 12.5:1 compression. Please post a link to the 9.4 car you speak of because I think its over 12:1. I also bet you had nothing to do with it as far as building it.

 

When a stroker is involved, a lot of low end TQ will be had due to the stroke and as a result, you can run lower compression because the loss of low end TQ from less compression isnt as big a deal. The source of this info is that when you factually drive a high HP car at 900+rwhp which 20psi would squarely put you in, the low end power will so far exceed your ability to get it to the ground (traction) that it isnt as much a concern. Understand that ultimately boost compression whihc is a function of both compression and boost (along with altitude) all go into deciding what build parameters you go with.

CFM produced from a head unit isnt a fixed vaue. When you talk about 14psi for example, that is reletive to the displacement. 14 psi on a 6 liter is like 10psi on a 7 liter.

The weakness on the LS7 its its pistons. If you change them, you will have reliefs that will drop the compression. If you dont change them you wont be near 700rwhp for long before losing a piston. 700rwhp is simply a cam and about 6-7psi which has been done many times on the LS7. Rockin Blue's build is exactly such a car minus the cam.

Search for a boost compression calculator online and play with boost level, altitude, and compression levels to see why power is made when cylinder pressures climb. On the same engine, if you drop compression too much and only boost a few pounds you will actually have less power and the boost compression calculator will show less boost compression in accordance with the observed power levels.

Yes, lower compression makes the engine less responsive in the low rpms and as Powerlabs showed there is a such thing as killing power so much with dropping compression that it adversely affects power. He raised his back up. Too little compression will make you need to spin your S/C faster to make more boost to overcome the losses. this will be accompanied by lots of heat being made by the s/c. If you have a power target, it would be best to make as much as you can on motor and then use the boost level needed to get your power without sacrificing your low end and economy to get there. spinning the s/c faster also wears it faster and the higher heat makes you more prone to detonation.

I think it will answer what you are thinking about by saying, the LS7 is limited to 650rwhp or so and stock compression can be used with the needed boost level to get you there which will be in the 6-7 psi range. Sometuners wont do anything on an LS7 without changing those pistons. If you really are intent on 20psi on a 427, it needs to be fully built and yes the compression will be in the 9's.