well the original poster wanted sum real world numbers from people other than tuners. so i gave it to him. im sure he dont care for your 2cents about my car and if u read a few posts up, sidestep asked me why my car dyned low. so i answered him the best i could

 

nope it looks like i broke the DTE's

 

I got on the list 2 weeks ago for some AFR 225's, to replace my stage 3 LS1 ported heads. Plus a cam upgrade to a 248/252 from a 242/242. Both are 114 lsa. Also the FAST 90mm intake and 90mm TB. Plus my exhaust needs to be rearranged a tad.

Hoping these upgrades give me a total gain of 40hp.

We'll see.

 

Actually, I care and want to know as do a great many other forum members. As far as the chances of someone on the forum having the answer I will almost guarantee it. Question, problems are answered here every day. That is what the forum is about, free exchange of information and experience...

Many would NOT post numbers they were not completely happy with. I think pdd is to be commended for being honest and posting his results and not just letting us think he got the expected numbers....

 

Damn... that's the second set of DTE 3.90s that I have heard go boom recently. Was that the first time that you hit the track with them? Street tires or drag radials?

Your power issue....I think your compression is one part of it, quench is another (again due to chamber height), and tune is a third. Cam may play a factor as well but I need more info on your install (LSA/ICL). Slowhawk does a great tune (he tuned my car as well) but runs a very conservative A/F. Most of these high dyno number graphs I am seeing are doing 13.5 or higher on A/F. I question how good that is for the street but that's what I have seen. I bet your A/F is more down in the 12.5-12.8 range. Rich but safe. That will leave some ponys on that table as well. I think it all adds up. I'm not sure the exact LSA/ICL on your cam but looking at the cams I see AFR 224/228 .581/.588 114+1 and you have 228/230 .575/.595 but on what LSA/ICL? I read somewhere that the F11 was a 112+4? What about the cam lobes on the FM? Are they as aggressive as the XE-R lobes? The lift numbers between the two cams are negligible. You have slightly more duration over all but the AFR cam has a larger split on the exhaust side (+4 vs +2). Your cam definitately has more overlap and it may be possible that you are getting a little exhaust reversion? What are the exact specs on the F11 cam?

In the end I think you can point to a bunch of little things that are being left on the table. 10HP here, 15HP there so on.
--Bill

 

[QUOTE=bletour2001]Damn... that's the second set of DTE 3.90s that I have heard go boom recently. Was that the first time that you hit the track with them? Street tires or drag radials?

nitto's

Cam may play a factor as well but I need more info on your install (LSA/ICL).

228/230 581/591 114+4

What about the cam lobes on the FM? Are they as aggressive as the XE-R
lobes?

there cam motion,not as aggressive as th xe-r

 

Well that stinks.. I hope DTE will back up their stuff for you.


Okay..so I think that may also be a small part of your HP issue as well. On a +4 you are giving up some top end power for a better midrange performance. It's a generality but usually correct. If we look at the Valve Events for your cam and the AFR cam we see:

AFR on a 114+1:

Intake Valve opens - IVO -1 BTDC
Intake Valve closes - IVC 45 ABDC
Exhaust Valve Opens - EVO 49 BBDC
Exhaust Valve Closes - EVC -1 ATDC
Overlap -2

Your FM11 on a 114+4:
Intake Valve opens - IVO 4 BTDC
Intake Valve closes - IVC 44 ABDC
Exhaust Valve Opens - EVO 53 BBDC
Exhaust Valve Closes - EVC -3 ATDC
Overlap 1

Even though you have a larger duration cam you can see here that the IVC events are almost the same. Your IVO is sooner but it is happening at a time when the piston isn't pulling much in. Your small amount of overlap can help "prime the pump" and I assume they are doing the earlier opening to get the valves into the .200 range sooner in piston downstroke. The more aggressive XE-R lobe allows them to open a little later but probably still get close to the same flow going. The AFR cam has slightly higher intake lift (.581 vs .575) to boot. Then your exhaust opens 4 degrees earlier as well which may bleed off a little power. We are talking small differences here but they are differences that will effect top end power. I almost wonder what would happen if you installed your cam on a 113 ICL like the AFR. Then look at the valve events vs the AFR:

AFR FM11

Intake Valve opens - IVO -1 1
Intake Valve closes - IVC 45 47
Exhaust Valve Opens - EVO 49 50
Exhaust Valve Closes - EVC -1 0
Exhaust Centerline - ECL 115 115
Overlap -2 1

Suddenly you will be pulling in a couple more degrees before IVC, your EVO and EVC become almost the same. In theory you will lose a little bottomend/midrange but pickup at the top end.

All in all I think it is a sum of many "little" things that are adding up. Have you overlayed your dyno graph on one of these "high" flyers? Do you have better lowend power then these guys or are you losing across the board?


--Bill

 

The compression difference could be some power but the Quench(this is a LOT MORE IMPORTANT then most believe!!!!! )Second the bigger cam at .050 don"t mean beans!!!What about the duration a .200???The AFR 224 cam may be bigger at .200???Like was mentioned a FAT afr could kill some good hp,take it to a different tuner!!!It could be any number of little things,I would pull those heads an check the quench and change gaskets to get the correct measurement(SAME AS TONY"S)mill them if needed.That last 37 hp is there to be found you are just going to have to look hard for it.
P.S.to compare combos and expect the same hp and tq the parts used must be the same,not similar.

 

Hey Bill,did you get those numbers from advertised duration?How do those cams compare at .200 lift?

 

no i i didnt. im thinkin maybe ill swap the cam to to the 224/228 like those guys are using to see what happens. also, what is quench?

 

pdd, thanks for your real world numbers. This is what I was looking for? I'm at 395rwhp with my combo now. If I got the AFR's and a new cam and didn't make 450+rwhp I would be pissed. I might as well spend twice the money and get a supercharger. With that I should be at 500rwhp.

 

Yeah I got those as advertised numbers at .050. I agree that .200 is MUCH more useful but much harder to find as well. We DO know that the AFR cam lobes are XE-R and have a faster ramp rate so I expect the .200 duration to be close to equal or even in the AFRs advantage. That being said I don't REALLY know how much faster the ramp rate is over the FM11.

--Bill

 

pdd,quench is the measurement between the flat top on your piston at top dead center and the flat deck surface of the cylinder head,you can change this by different gasket thicknesses..035 to .040 is optimal with steel rods.This helps control detonation and promotes a faster flame travel after the sparkplug fires for a more complete burn of the fuel\air mixture=more power!!It also mixes the fuel and air as it focres the mixture from these areas,this is called squesh (I don"t know if I spelled it right?)I think the cam you have is OK,its very similar to the AFR 224 cam.Maybe change the ICL like was mentioned so it will be closer to Tony"s cam.Those 2 things are what I would try first! Didn"t Tony mill his heads a little?If he did then you should too.
What kind of oil are you using?Maybe get synthetic lubricants for the tranny and rearend.I noticed one guy said your AFR was a little rich,I would check that too!Its going to be the little things that get that 37 hp you"re looking for.P.S.I hope you do!!

 

Very good points above. If you don't understand things like quench, and how to degree a cam, it may be in your best intrest to seek professional help in installing things like camshafts. The reason I say this is that you may not get the results others who have checked these things have.

Too much or too little quench can cause detonation for one thing. You'd think that too much quench would hurt you, but you're wrong. Folks often think they can drop compression by using a thicker head gasket. In fact they often are in worse shape with detonation than if they had stayed with proper quench height.

There is more to putting a cam in than going dot to dot. I know Tony for instance spent one whole evening playing with his degree wheel trying to optimize valve events on his cam. You might say "So what does that mean to me" Well, look at Tony's numbers, and look at yours. I'm not trying to be ugly here, but folks attack Tony and LAPD since they can't just slap parts on a car and duplicate the numbers. Yet they haven't done their homework, so Tony and LAPD must have a "ringer" dyno. Face it, this is why some "shop" or "tuner" cars make power. The guys who know what to check are checking it, while other just throw it in and go.

Now, with that said. We must also address the dyno. Dynos vary. So, when you look at dyno X and try to compare it to dyno Y you are making a mistake. The only way I'll do that is if I can take a car to both dynos and quantify the delta. Like LGM and MTI. I know how much the dynos there vary to one another. Use a dyno like a flowbench, quantify your delta. If the dyno reads low, your delta will still be about the same as if it was a high reading dyno. Then check it out at the track. Remember, we don't race dynos...

If you really want to feel bad about your car, go put it on a Dyno Dynamics Eddy-Current dyno. It reads 10-20% below a Dynojet 248c. Same car, no changes... Thats all the y use in Australia which is why those guys never post dyno numbers. They don't sound impressive (till you know how much of a conversion factor to use). Once you know then you go "OH".

Let me pass on a bit of wisdom from Lawrence Conley. When we were discussiing cars someone asked him how to make a car go fast. He said " The hundreths add up to the tenths, the tenths add up to the seconds..." in other words when you optimize your combo and don't overlook the easy things that cost power you'll find you'll pick up time.

 

[QUOTE=FASTONE]pdd,quench is the measurement between the flat top on your piston at top dead center and the flat deck surface of the cylinder head,you can change this by different gasket thicknesses..035 to .040 is optimal with steel rods.This helps control detonation and promotes a faster flame travel after the sparkplug fires for a more complete burn of the fuel\air mixture=more power!!It also mixes the fuel and air as it focres the mixture from these areas,this is called squesh (I don"t know if I spelled it right?)[\QUOTE]

FASTONE is correct... but I find life easier with pictures. Maybe cause I'm slow! Anyhow... to (hopefully) make it more clear lets look at these two pictures:

A quench style chamber for the LS1:



Now think of the flat top piston coming up towards that chamber. The diameter of the piston is larger than that chamber. So parts of the piston will actually extend beyond the chamber area and will compress the air/fuel up against the flat part of the cylinder head. The effect of that is like stepping on a tube of toothpaste. It smooshes/squishes the air/fuel into the chamber area and causes turbulence as it does it. This has the result of mixing the air/fuel better and getting cleaner burns.
For clarification look at this side view:


So the flat area is squished into the chamber area.

So..that quench area is the height of the piston top to the bottom of the head. (Basically head gasket size +/- the piston deck clearance)

Does that make sense?

--Bill

 

wow. thats for the great info guys

 

The mixture trapped in the quench area does not burn,therefore it is to your advantage
to minimise that distance.Because the volume of mixture trapped there does not contribute to power .The limit is unfortunatly found by trial and error at redline.So does any body go lower than .030????

 

How exactly can too much quench hurt you/cause detonation ?
Thanks for that info.

 

Quench is not a matter of trial and error. You will find most engines in the size like about a .035-.040 quench. Any more and you don't get proper turbulence and thus you have poor flame propogation. This can actually lead to more detonation than you'd see with less (although proper quench). Too little quench can have the same effect.

Her eis what Speed-o-motive has to say:

There isn't a universal set of rules that govern all engine building. The following is information that has worked successfully and should be considered when building a performance engine.

A high performance race engine, by its definition, indicates that limits are going to be pushed. The limit that is of most concern, as far as pistons are concerned, is peak operating cylinder pressure. Maximizing cylinder pressure benefits horsepower and fuel economy. Considering the potential benefit, owners of non-race engines, from motor homes to street rods, also look to increasing cylinder pressure. Increasing the compression ratio is one sure way of increasing cylinder pressure but its not the only way. Camshaft selection, carburetion, nitrous and supercharging can all alter cylinder pressures dramatically.

Excessive cylinder pressure will encourage engine destroying detonation with no piston immune to its effects. The goal of performance engine builders should be to build their products with as much detonation resistance as possible. An important first step is to set the assembled quench distance to .035". The quench distance is the compressed thickness of the head gasket plus the deck height, (the distance your piston is down in the bore). If your piston height, (not dome height), is above the block deck, subtract the overage from the gasket thickness to get a true assembled quench distance. The quench area is the flat part of the piston that would contact a similar flat area on the cylinder head if you had .000" assembled quench height. In a running engine, the .035" quench decreases to a close collision between the piston and cylinder head. The shock wave from the close collision drives air at high velocity through the combustion chamber. This movement tends to cool hot spots, average the chamber temperature, reduce detonation and increase power. Take note, on the exhaust cycle, some cooling of the piston occurs due to the closeness to the water cooled head.

If you are building an engine with steel rods, tight bearings, tight pistons, modest RPM and automatic transmission, a .035" quench is the minimum practical to run without engine damage. The closer the piston comes to the cylinder head at operating speed, the more turbulence is generated. Turbulence is the main means of reducing detonation. Unfortunately, the operating quench height varies in an engine as RPM and temperature change. If aluminum rods, loose pistons, (they rock and hit the head), and over 6000 RPM operation is anticipated, a static clearance of .055" could be required. A running quench height in excess of .060" will forfeit the benefits of the quench head design and can cause severe detonation. The suggested .035" static quench height is recommended as a good usable dimension for stock rod engines up to 6500 RPM. Above 6500 RPM rod selection becomes important. Since it is the close collision between the piston and the cylinder head that reduces the prospect of detonation, never add a shim or head gasket to lower compression on a quench head engine. If you have 10:1 with a proper quench and then add an extra .040" gasket to give 9.5:1 and .080" quench, you will create more ping at 9.5:1 than you had at 10:1. The suitable way to lower the compression is to use a dish piston. Dish (reverse combustion chamber), pistons are designed for maximum quench, (sometimes called squish), area. Having part of the combustion chamber in the piston improves the shape of the chamber and flame travel. High performance motors will see some detonation, which leads to preignition. Detonation occurs at five to ten degrees after top-dead-center. Preignition occurs before top-dead-center. Detonation damages your engine with impact loads and excessive heat. The excessive heat part of detonation is what causes preignition. Overheated combustion chamber parts start acting as glow plugs. Preignition induces extremely rapid combustion and welding temperatures melt down is only seconds away!

 

I don't think it doesn't burn as much it creates a space for end-gas (which of course is the cause of detonation in the first place).