Dyno loss.

[Chris]

I have read that rear wheel numbers on a dyno are about 15-30% off of crank HP. I am trying to figure out the total crank power I have so I am curious if someone can chime in on what the loss is closer too. If its 20% I'm sitting at a hair over 400 HP. If its 15% Im a touch over 380 HP. I'm getting 325.1 HP to the wheels.

[Badass69]

Well....... You have to take something else into account too. What brand of dyno was it you were tuned on? DynoJets always read higher than anything else...... and Mustang dyno's always read much lower. I am going to take a wild stab you were done on a dynojet. You could have dynojet and a mustang side by side on the same day, same car and same conditions and you will get two completely different readings.

 

A 2wd truck with a 4L60E and 10 bolt is probably up around the 18-20% mark for loss though. 400 Hp isn't unrealistic for a tuned/ bolt on LQ9 either.

[Chris]

Mustang 1100 SE was the Dyno I believe. They also have a DynoJet 248.

 

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[Chris]

My math with a 20% loss should be around 405 HP and 450 ft lbs. Seems a little high to me but I am also still running a 3.42 gear

 

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[Badass69]

Torque seems kinda high..... but maybe. Horsepower is completely possible. GM's factory tune in both the LQ4 and LQ9 allow for ridiculous amounts of improvement.

[Chris]

I know my timing is ridiculously advanced

 

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[Badass69]

Yeah mine too. I tuned my 05's LQ4 myself and I see around 28 degrees of advance at WOT now...... And although I have it my head to run it on premium only it actually runs fine with zero knock retard on regular old 87. My compression is 0.6:1 lower than you but otherwise it's the identical engine anyhow except for the pistons. Stock on a LQ9 is around 20 or 21 degrees I think wide open.... maybe on the high octane spark table. Stock on my LQ4 was a whopping 17 degrees. It's funny thinking that even with that little timing they still rate the LQ4's at 325 or 330 hp depending on the original application. The 300 HP in the HD trucks is bunk as it's rated at only 4400 rpm.... whereas the same engine in anything else is rated at 5200 and my stock shift points in either of my trucks ( 05 1500 HD and 04 light duty 2500) was 5200.

[Chris]

My shift points are at 6500. I have to run premium according to the tuner. The dyno run was on regular but I was told to immediately fill with premium. 345 HP to about 405. I'm not complaining. I'm interested to see what it will do with the LS3 heads, cam, and the FAST LS3 intake manifold. I know my truck doesn't go into first now unless needed. If I get on it it will take off in first. If cruising it short shifts to second.

 

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[Badass69]

Wow...... 6500 on the stock cam and springs is a little scary. Mine is 5700 in first and then 5600 in 2nd and 3rd and my limiter is 6 grand. We have the same camshaft and mine really feels like it is doing nothing beyond the 5700 mark...... I had it at 5800 like Blackbear sets it too and it was too high IMO.

 

I would maybe look into a set of cathedral port heads like some worked 243's over the L92 stuff myself. You lose quite a bit of low end power with the rectangular ports. A set of ported cathedrals easily flow what the L92's do and don't suffer quite as bad on the low side.

 

I myself just like forced induction, lol.

[Chris]

It may be 6000. I am going to LS3 heads. The tuner said they flow better than cathedral ports. Cathedral ports need a nastier cam to be able to flow like the LS3's. I will be doing forced induction as well. One step at a time. I am going to do my heads/cam/manifold after i get a new tranny. then later I'll be doing a Procharger D1SC with 6-8 lbs. And If they can do a Meth system that can be removed when emissions test time come around I will have that done. They had 06 regular cab with a 408 stroker/LS3 heads/Procharger F1/nasty cam/meth injection lay down a 850 HP dyno run while I was there waiting for my truck to get on the dyno.

[Badass69]

They do flow marginally better as I said..... they just produce nothing for low end power. In your truck I guess that may not matter quite as much as it should be light enough. Start getting heavier and that is where it becomes more apparent. You can run a smaller duration cam with them as they do flow more.

 

Quite a few turbo'd cathedral headed trucks with tiny cams are making over 1000 hp. It's crazy what these engines can really do.

[Chris]

The tuner I see is the LSx guy in town. He even had some fox body's in there with LS6 and LS7 swaps. I want to be around 550-600 rwhp.

[BlackZ71Silverado]

My math with a 20% loss should be around 405 HP and 450 ft lbs. Seems a little high to me but I am also still running a 3.42 gear

 

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That engine will not put out 405HP without work. If you want an accurate Crank HP reading, it needs to be measured from there not play guessing games with the rwhp numbers. As far as the 6500rpms shifts, it will only be a matter of time before you brake so BE CAREFUL!

 

You can get yourself a good set of heads that are already machined for a high lift cam and would come with the correct valve springs to match from a race shop. It's usually cheaper to buy it that way than it is to take to a machine shop and order valve springs alone at around $280 for springs only.

 

Nothing worng with the cathedral port heads. Whatever you decide to do, make sure that yo uhave proper timing chain, gear and tensioner OR you will have a very noisy timing set, probably won't last very long either.

[Badass69]

That engine will not put out 405HP without work. If you want an accurate Crank HP reading, it needs to be measured from there not play guessing games with the rwhp numbers. As far as the 6500rpms shifts, it will only be a matter of time before you brake so BE CAREFUL!

 

You can get yourself a good set of heads that are already machined for a high lift cam and would come with the correct valve springs to match from a race shop. It's usually cheaper to buy it that way than it is to take to a machine shop and order valve springs alone at around $280 for springs only.

 

Nothing worng with the cathedral port heads. Whatever you decide to do, make sure that yo uhave proper timing chain, gear and tensioner OR you will have a very noisy timing set, probably won't last very long either.

 

 

Yes a full bolt on and tuned LQ9 will make 400 crankshaft horsepower. If you don't believe you can look into it for yourself........

 

Otherwise I mostly agree lol.

[Chris]

I don't think I'm at 405 HP. But the math is right. I'm not pulling the engine to check. I'm letting the shop who did my engine tell me what's best. They sell heads. He recommended the LS3 heads with dual springs, ported, and a Comp custom grind cam. After I get the tranny I'm going to go all out. I am worried about rwhp. But was curious of fwhp. I figure between 380-405. Only things done to it are intake, exhaust, and an aggressive tune. My shift points are probably 6000 if 6500 seems high.

 

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