SCannon

"Posted Dyno Sheets on page 2"
I have seen alot of posts questioning FI on high compression engines. I figured I would add my results.
402ci (Built By Dave Diluca)
11:1 Compression
AFR 225's 65cc
242/250 600/600 Camshaft
Morel Lifters
Jessel Roller Rockers
78mm FAST Intake
P1-SC
4.5 lbs Boost (4.25 Pulley)
Old Style Bracket And Twin Intercoolers.
Old Style Rectangular Air Filter in the Fan Bracket
14* Of Timing (for now)
Mustang Dyno---- 630 RWHP 540 RWTQ
Mustang Dyno--N/A 490 RWHP 460 RWTQ
Mustang Dyno---- 660 RWHP 560 RWTQ With BAP installed

This was just the initial "safe" tuning. I have the Racetronix Fuel Pump/Wiring Harness and a Return Style Fuel System. Fuel pressure starts off at 58 psi and increases just over 60 psi then starts to fall off to around 50 psi. They are installing a BAP for me then they are going to finish the tune. +140 RWHP and +80 RWTQ from 4.5 lbs of boost on a conservative tune. Im happy with it because I got the complete blower kit brand new DIRT CHEAP....

Shawn

0FRCBobby

Very interesting. I love seeing people try something different.

YELLOHHH

I get the whole "road less traveled" thing, but if you dropped the compression and cranked the boost, you'd make a ton more horsepower. So, what's the point exactly?

Chris Stewart

Pretty strong for 4.5psi. No meth? You know it's gonna be snappy off the boost.

I can't wait till you push it and hear the results at 10psi. The blower might run outta steam on a 402? Good luck!

easyvette

Be interesting to see what a big front mount and some alky does to the mix?

Just thinking whats the stock compression of the LS2 motors and some are boosting those pretty good?

NemesisC5

LS2 10.9:1 CR Even at 8-9psi he should be close to 700rwhp!!

madmatt9471

Those are some pretty good results and very friendly on the motor!

I have almost the same numbers on my 347 but with less compression and more BOOST!

Thanks,Matt

undertaker

nice job shawn..

thought of offing those heads for some ported truck heads with bigger chambers? might make things a lil more interesting

SCannon

Well, those numbers are on a Mustang Dyno which are normally 10% lower than a dynojet. I plan on leaving the setup the way it is. I already had the high compression engine for a couple years. I had a NOS system on it that I was tired of playing with. The blower kit was brand new and vvvvveeerrryyy cheap, thats why I did it.

MIKE-C5

allullc

We discussed this on another forum... here is some GREAT info from Billy at RPM racing on this subject...



Whether it be actual engine failure or apprehension there of, one turns to the “built motor” or “forged bottom end”. The part about the “built and forged” motor is what kills me. Most engine builders and parts manufacturers will automatically recommend a combo to lower your compression ratio while supplying and recommending forged components.

So let’s get this straight………(example)

One had a 40% gain at 10:1 CR and at 6psi of boost. A factory rod that was rated well under ones HP level has failed because it couldn’t take the stress. The general consensus is to build forged @ 9:0 CR.

WHY?????

The problem to begin with was the parts used--not the compression ratio. Now you upgrade those parts to handle what you’re doing and beyond and for some reason you’re going to lower the CR in the midst of it all? Where you were making 550 RWHP with 6psi @ 10:1 static CR, you are now making 470 RWHP with 6psi @ 9.0 static CR. And now you have a bottom end that will withstand much, much more. At this point you spend more money in smaller pulley’s or you adjust your boost controller to get more boost just to regain your before 550 RWHP. In order to go beyond that point you have turn those blowers even harder or cap those turbo’s a lot later. In the midst of it all, you’ve surpassed the blower or turbo size and although you see increased boost pressure, you’re at the peak of the cfm flow and raised your IAT’s significantly. Not to mention that now you’re out of injector and have more cylinder to fill.

I don’t get it. Someone please explain to me the part I’m missing.

If you have a stock engine with 10:1, boost of 6psi, and see 500 RWHP. Then when you build your forged engine for the same setup, build the engine (stroker or not) with 10:1.

On the stroker forged engine, because of the increase in swept volume, the dynamic compression will be higher and you will see more HP at the same boost levels with an S/C………….on a turbo setup, the turbo(s) will spool quicker.



Some more...

12:1 and even 13:1 on the street and on 93 octane N/A is also easily done with gobs of power by utilizing the CR as intended. It is even "boostable" in street form to a degree. Most say it's unsafe and that you can't run enough timing to gain from it's potential.

12:1 and higher compression ratio's along with 20+ lbs of boost in the racing world is pretty common. And a lot of guys are doing it on 93 octane, with 32 degree's of timing and running 6 second 1/4 mile times. Granted, these engines are running O-ringed blocks or heads and copper head gaskets with are unsuitable for the street.

What about detonation?

Insignificant amounts exists and all is made possible, once again, from getting away from "old ways of thinking".

In short.......detonation occurs when the fuel burns too quickly in relation to the piston and crank position as most of us know. We retard timing to slow the point at which the fuel is ignited to better time the burn with piston/crank positioning. This doesn't slow the burn speed of the fuel down, we just delay the ignition of it. A better solution IS to slow the burn speed down and is why higher octane/slower burning fuels are sought out and used.

Forget the racegas unless you're running ridiculous cylinder pressures. The engine build and configuration can take almost full control of fuel burn speed.

It is still believed today that the ideal quench should be no more .045 in most engine applications. Any tighter brings forth a "wow" and anything over people start screaming "it's going to detonate" and that you need to keep the quench nice and tight. In all actuality, the opposite applies. The tighter the quench and the more quench area there is, the faster the fuel will burn. This has nothing to do with compression ratio but by the amount of quench and the area of it only. It is quite easy to make 93 octane burn as fast as 87 octane. 12.1 + .045 quench + 93 octane = detonation. The quench amount and extended area speeds up the flame front and this is the very thing we need to slow down.

A good solid engine build and configuration with high static compression ratios with or without boost/N2O should have a minimum of .070 and as much as .140 quench depending. Quench area's should be a minimum and only on the spark plug side of the cylinder to get the flame going.

Does .070 to .140 sound ludicrous to you? If it does then you are way too 'old skool' and need to get with the program.

Serious race cylinder head combustion chambers of today are configured to have this very little quench area. Stupid race cylinder head combustion chambers (ProStock, ProMod, Top Fuel, etc) are configured to have nearly a non-existent quench area........but just enough at the right place to help induce the burn process.

12:1 + .080 quench + 10 psi boost + 28 degree's timing + 93 octane = detonation free daily driver.




And one to really think about...

What's the different between making 550 horsepower at 9psi and making 550 horsepower at 18psi?

The S/C or turbo and engine is working much less to achieve 9 rather than 18. There is less air compressed at 9 than 18 which results in lower IAT's. It takes the exact same cylinder pressures to get the 550 horsepower regardless if it comes by way of 9psi or 18psi. 18 takes longer to achieve than 9. The list goes on and on......


Looks to me like Shawn just might know a thing or two about the road less traveled. Great job

Vega$Vette

^ What he said in simple terms.

Why would you think that lowing comp and turning up boost would make more HP?

Power is made by increasing cylinder pressure. So if higher Comp and lower boost it's pretty much all the same.

Difference you have a much stronger running machine when you are NOT in boost and the power tends to come a little quicker when you get into boost.

btw I run 10.9 comp and 5.5 psi on my Maggie which helps keep the heat down as well. NA I made 407 rwhp. Had I lowered comp to 9 I'd only be making about 325 when not in boost (sorta doggie) and most of us spend most of our driving time NOT IN BOOST

black98c5

SudburyC6

You have to love them 402's built by Dave and CDN Performance...great numbers with only a P1....time to strap on a F1..F1C or F1R....


Ron

SCannon

Thanks for all the feedback guys. I have run superchargers on several other vehicles I own and have owned in the past. I ran the high compression N/A engine because thats what Dave had. I had the oppertunity to get a brand new Procharger at a deal and jumped on it. I will also be able to get rid of my HSW plate and several other NOS related components that I had on my car. I sold my Tony Mamo ported FAST 90, sold my stock LS2 90 TB, and that paid for over half the price I got the blower for. Once I sell all the NOS items the blower would be paid for by the parts I removed Over 140 RWHP more by swapping some parts.

NemesisC5

Great Post

STAGED

This is nothing to take away from Shawn's car which looks like a super winner.

This is just a post on the topic itself.

AS YELLOHH CORRECTLY STATED, lower the CR, run more boost is tried and true. Car makers do it (look at the CTS-v supercharged). Believe me if GM could run 10.5:1 CR on their new boosted CTS-v, they would do so in a heartbeat considering how important CAFE means to companies like them. Do you think for example single-turbo 2JZ Supras on 93-100 octane fuel would run hard if it's CR was 10.0:1 from the factory instead of 8.5:1?

Sure lowering CR has a slew of compromises including making less efficient use of the charge, but it's to leverage two things: run more boost and airflow and widen the tuning window.

A high CR motor (even more so with a big bore) with boost has a narrow tuning window. The state of the motor will shift over time due to degradation (injector spray pattern, carbon deposits, fuel pump degradation as crazy Mustang tuner Lidio of Alternative Auto mentioned, etc.). There are countless examples (LS1 setups included) where the car with high CR for given boost comes off the dyno with 0 knock retard, only months later to be "jiffy popping" or come back wity broken ring lands.

I've seen OEM graphs of tuning (not related to peak WOT runs) vs. degradation. This is a real issue. The OEMs with all their sophisticated tune their motors for that right balance of safety and longevity a "zillion" times better than aftermarket. Even with those tools, look how conservative they put CR for given port-injected boosted motors.

Now imagine running a less sophisticated derived aftermarket tune, using aftermarket HD low silicon content forged pistons and other components (good deal of carbon deposition over time vs. OEM cast piston setups), "not-so-wonderful" aftermarket component quality control, etc. and you can see why there's an even greater need to run more conservatively on CR because of the fast shift in the motor's state over time and likely to step out of that tuning window too soon. As for quench, if one doesn't deviate too much from OEM that's good because OEMs do tons of R&D to make sure detonation resistance for given conditions is high as possible for the low rpm / higher load drive cycles which are one of their higher objectives in making sure is as close to ideal as possible. All the debate is good when doing a ground-up race motor for one's own application, but it's tough to pin down on a new age EFI motor whose R&D has been thought out and who the hell will try to quantify all measurement paramenters for the combustion flowfield of a modded version of a new EFI motor even if someone had the time and $ to do so.

Quench is a good topic to talk about but flowfield matters at the time of combustion. So the charge flow runs through the ports and enters the combustion chambers. Depending on the chamber design and even port features, one wants to get a lot of large scale coherent motions (tumble and swirl). These motions preserve the kinetic energy of the flow pretty well. When the piston goes back up to TDC, these large scale motions break up into high energy random turbulent motions that help speed up combustion. Speeding up combustion helps deny abnormal combustion tendencies from taking hold. This is a major topic of conversation. I saw at an engineering supplier Ricardo (do all powertrain stuff including powertrain integration of the Mini to the Ford GT transmission, etc.) an apparatus for visualizing tumble. There's a paper by General Motors discussing the entire mechanics of these motions. Ray Bohacz, tech editor of many aftermarket mags., was one I communicated about on good heads (not from a flow standpoint) based on the paddle wheel rpm measuring swirl for lower abnormal combustion tendencies. Toyota and Ford have port flaps on some motors that force flow on one side of the runner to set up these tumble motions (granted these flaps are not for high rpm WOT max. flow) to speed up the burn rate and reduce abnormal combustion tendencies for given conditions and calibration.

But how would a typical aftermarket shop/engine builder quantify all this? There's no way and there's so many factors that it's tough to isolate one variable like quench or chamber design and run with it. It's different from motor-motor. That's why it pays to run conservative with CR for given boost going aftermarket. After all I know one C5 owner who's trapped 127.96 mph without running race fuel on a non-intercooled 9.7:1 CR Magnuson (6-7 psi) in somewhat greater than 0' DA and the OEM cast piston lower end still lives after several years while higher CR competently tuned setups running slightly more intercooled boost have been reported to fail mechanically.

Of course, if you're Saleen, you can run 11.0:1 CR and run 5 psi TT boost (that combo is one of several offered). I spoke with the engineer there long ago and he told me their CNC heads are very precise from chamber to chamber. That means 11.0:1 is not 11.0:1 give or take 0.2 points from cylinder to cylinder. That plus their access to advanced tuning tools/testing methods keeps the tuning window as wide as possibly could be. Such a setup would be very good when running off-boost from a throttle response and fuel-efficiency standpoint. For such a road racer, it'd make sense to keep turbos small, displacement large, and make the most out of the incoming charge flow with high CR.

You may see some Japanese cars (think S2000) running crazy boost for given compression ratio and octane, but remember that motor has a small bore and it's running high engine rpms on a centrifugal S/C which won't make those high boost numbers until revs are high (and there's a lot of turbulent in-cylinder flowfields).

In the end, all that I say doesn't matter. What counts is the owner enjoys the ride and stays safe.

0Rob@ChampionMotors

Your fuel system is at its limit. Your going to need a double pumper or a larger single pump.

SCannon

Which fuel pump or pumps would you recommend? Changing a fuel pump on these is soo easy its sick..... I was also thinking about going with larger fuel rails...

Thanks

allullc

STAGED, Very good points and even some new info in there for me to absorb, defintely a good read! I was pointing out that it's not some off the wall concept to use FI on higher compression engines. Just as Vega$Vette is another example of many on here. It's really not all that uncommon to see a centri-blower or roots blower on a LS based engine making good power at a lower psi. I guess what gets me is when someone decides to put a build together, drop there compression so low and then use the blower or turbo they had before and spin to high hell and wonder why it's not making earth stopping HP. Only to find out they're pushing hot air into the engine due to being completely off the compressor map of that blower or turbo. Just things like that ya know, but as you said...

"In the end, all that I say doesn't matter. What counts is the owner enjoys the ride and stays safe"

Scannon, on the fuel system, I would say look into a doule pumper, upgraded rails, and injectors. Maybe something like either of these: http://www.nastyperformance.com/Corv...elSystems.html

http://www.lonniesperformance.com/Default.htm