It hurt to even type that in jest but how many of you have read (or currently subscribe) to that theory potentially now?? (the next thing you read is this is because the blower pushes the air through the engine!)

I know I have seen it typed in some form or fashion in the various automotive forums I frequent....many times over the years on this forum in fact and I will stop in occasionally to try and let people know that couldn't be further from the truth but it's kind of like shoveling sand against the tide at times or at least it feels that way after you see the same bad information repeated over and over.

Anyway....the reality is that the statement I titled this thread with couldn't be further from the truth and I have mentioned exactly that in a handful of threads that I tried to take the time to set the record straight mentioning in fact that just the opposite is true. The gains with an efficient and well designed set of heads are actually amplified with boost and I recently helped a customer (who will remain nameless) with one of the finest heads I offer specifically designed for boost or nitrous (my MMS 235 NFI head) and we now have a glimpse of what that comparison looks like. In fact these are just what I would call preliminary results at the moment but even where they currently stand show just how insane the potential gains actually are with what isn't much more than a head swap.

Full disclosure...besides my heads, my customer also installed my 10mm YT Pro rockers (same 1.7 OEM ratio however) in an effort to extend the usable life of the premium heads he just purchased (OEM rockers sideload guides and scrub across the valve tip dramatically decreasing the service life of your heads) as well as upgrading to a better quality lifter (Johnson limited travel.....these are the mid grade offering from Johnson not the expensive short travel lifters).

Everything else essentially remained the same

The engine was a 408 cubic inch shortblock with an F1A blower. Chamber volume of the LQ9 heads and my MMS 235 NFI heads remained the same netting 9.5:1 both before and after. Texas speed 1 7/8 headers were fitted with their 3" true duals. Fast 90/90 both before and after which I believe was unported. The numbers are through a T56 and an S60 rear end. Per my customer a "Truck hat inlet" for the blower was utilized....Im not even that familiar with that item. All of this was in a 4th Gen FBody.

So to be fair we are looking at more than a direct heads swap as we have to factor in a small part of the gains might have been from the better lifters and the roller rockers, but with the lower RPM's featured here I don't think either of those two items were worth a whole lot considering the baseline test of this engine looked to have perfect valve control. Even if you want to say 10-20 TQ and HP from those two items may have been present (20 a bit generous IMO) the results are still quite eye opening. So what is a clean sheet premium head really worth on a boosted engine with a sizable blower and an appetite for some air??.....on this one well over 100 ft/lbs of torque at the exact same boost level) and close to that in horsepower as well!!

Not the easiest dyno graph to read
The dashed blue line is the baseline run torque curve.....the dashed red line is the baseline run HP power curve.
The MMS 235 heads are represented by both solid lines.....blue being the torque curve and red being the HP power curve.



The owner of the car still has some work to do as the engine seems to be limited somewhat at the higher torque and power numbers.....you can see them diverging closer and the huge gains on the bottom (125 RWTQ at one point) is tapering off towards the top.....clearly there is some restriction of sorts as this set-up should carry better than it does on both applications with that size blower. Im not sure if there are some intake air temp issues from a poor intercooler arrangement.....I honestly don't know much more about the combo than I've presented in this thread but if this doesnt drive home the importance (and huge value) offered in spending a few bucks more for a better set of heads....well....you can lead a horse to water but cant make him drink right.

Btw.....I should mention this wasn't a test against an unported set of OEM LQ9 heads.....its actually a pretty popular "2.5" ported OEM head....which makes the results and the comparison even more relatable to some and that much more noteworthy.

Its late....as usual for me....so Im going to wrap this up. I erased the customer's name from the dyno sheet per his request as he has some friends (and foes) he wants to surprise packing a bunch more heat so unfortunately he wont be able to join the discussion unless he has a change of heart. I needed to respect his privacy (which I did) and Im glad he gave my the authority to post and talk about his results. Hopefully a few of you guys see this as a wake up call

Cheers Guys

-Tony

PS.....Pics of the new heads installed and the finished product as it currently sits

 

 

TFS 235's

 

 

Thats why I keep two crescent wrenches. One metric and one imperial. Need the right tool for the job.

 

Nice write up Tony. We've talked about this a lot. And it's true, some people can just throw a few more psi at it but the point is that it's said over and over that the heads don't matter for boost. And obviously here they mattered a lot. To each their own for sure. If you're building just a chill street cruiser that's one thing. But it sounds like this customer races so the build definitely fits, especially for grudge style racing. It's nice to pull up and everybody expect the average build and it's not

 

Informative post as always

BTW, did his boost PSI go down at all while making the additional power?

 

Thanks for the info & write up Tony. Awesome gain in tq/hp. Something does seem to be off/going on in the setup. Really don't even remember seeing many, if any, centri blower setups making more tq than hp. How the tq starts to drop past say 48-4900rpm. If he's only revving to 5800-6k I guess it's ok. Maybe one of those blow off valves set to not go past a certain boost?

Great A-B compare. Minus lifters & roller rockers of coarse.

 

I was wondering the same. Due to less restrictive heads.

 

I was wondering myself if the restriction is in the exhaust. Maybe hitting the limit of what the exhaust will support?

 

My thoughts were not really on the exhaust. As that could be a factor at this power level. 1 7/8 headers with TSP 3" true duals. Thinking the TD setup is the x-pipe dumped. Maybe it is an over axle setup that may be a factor.

The first thing I thought of was the FAST intake manifold. Being two piece I think they have their limit with boost pressure. Maybe a lil leak past a certain PSI? The other thing was crank case pressure. I see one catch can & don't know if it has vents to disperse the pressure being made at that power level. Just Ideas/thoughts. Hope the customer is happy & gets it all squared up.

 

I agree. Tony is technically correct is his argument, HOWEVER, the thread title absolutely can be correct when taken in context, which it was not.

 

I saw the title of this and thought "oh man not another one of these"... Then saw who posted and thought wait a second, haha!

Great post with good info!

 

You really think a few more pounds of boost would even get you close to the gains seen here.....its the point of diminishing returns and there is only so fast you can spin a blower and have it keep making power. More boost is more heat and much less efficiency.....higher IAT's and a much smaller window of error in the tune. Its really easy to detonate and lose part of a ring land at 20 PSI than it is at 14 PSI.

Consider for a minute how much is invested in the car set up similar to the example I highlighted in this thread.....the cost of a blower kit.....all the plumbing and time involved thus far just to build it (thousands of dollars if you didnt tackle it yourself). The cost of the cam/valvetrain and exhaust upgrades....now its time to buy heads and you would let $1000 or $1500 net difference get in the way of these types of gains because you can add boost with a smaller pulley and see a fraction of the gains demonstrated in this comparison at higher boost levels?? Your probably talking about a 10 or 15% addition to the total project budget (the cost difference in a premium head) getting in the way of increasing output by 50% or more with the better heads making a bunch more power and doing it more safely on lower boost. Not spending the money on better heads is really short sighted thinking in an industry/hobby where the next cost of an upgrade to find more is always right around the corner. Leaving these kinds of gains on the table for the cost difference we are discussing.....I think that would be the worst money ever saved if your serious about getting the most from your build (but I sell horsepower and I am constantly evaluating the cost per pony). Sometimes in life (usually in life actually) you have to spend a little more to got a lot more....this is just another example of that.

Guys.....I should have mentioned in my original post that a smaller pulley was required to get the boost level the same in both builds. Im sure a good bit more power was made at lower boost with the same pulley but the blower speed needed to be increased to make the same boost value (aka "measure of back pressure") with the deeper breathing MMS 235 NFI heads but boosted engines should always be compared at the same boost levels to keep things on an even playing field. Its like comparing two race cars.....if they aren't racing in the same quality of air (Density Altitude) its not a fair comparison unless you mathematically correct for the car that ran in poorer conditions.

Also Im annoyed with myself right now because I received more data from another customer a few months ago very relate-able to this thread but somehow I misplaced it. Basically another customer that saw huge gains with my 235 NFI heads but he kept the same blower speed (didnt swap pulleys) and made a good bit more power at 2-3 PSI less and was happy just leaving it there. If I can round up the data I will post it in this thread also.....it just once again backs the point I was trying to make all along

Yes.....I agree.....its more common with positive displacement style blowers and small cams.....but even those units make a little more HP in a decent set up.

I think there is alot more on tap here once that's figured out the the gains in HP are going to be exponential


Good stuff to ponder over.....

Catch you guys soon

-Tony

 

Youre using the 5% to disprove the 95%. Most have more impeller speed left and have IATs in check either with a properly sized intercooler, meth, or E85....so yes you really can just run a smaller pulley or turn the wastegate up another 3 or 4 psi and see the same gains without spending thousands on heads. Typical boost setups gain 25-35whp per psi and that is acknowledging that timing must be reduced at the higher boost level. On turbos backpressure can be a concern, but centriguals are hilarious....smaller pulley or higher rpm and the power goes up assuming the blower isn't maxxed.

Yes there are limits and yes for max effort good heads all the way, but in most instances for street cars, just up the boost.

 

With a Fast intake, there comes a point where cranking up the boost may blow the intake to bits.

 

Best thing you can do when going boosted is sell that intake and put the money towards boost stuff.

 

Great post, well said!

 

If you want the best and most efficient set up, you need optimal flow characteristics. Yes you can just up the boost...but you're just overpowering a sub-optimal set of flow characteristics. It works, and it may be the set of compromises you're willing to live with, including bang:buck, but it's not ideal. Do you need magic massaging to get more ponies? Of course not, cranking up boost is easy and generally effective up to a point. However, most that go to Tony are looking for high power and fewer compromises, which is why he charges a premium and so often gets high numbers/ci along with good manners.

Yes, many head companies are offering a "one size fits all" and IMO they do so legitimately. You can offer a good port & runner design and balanced port job on heads and it will likely benefit any set up you put it on over stock and/or unported, but it likely won't be optimal for any of them either, unless you get lucky and match the R&D set up. Tony proves this is valid as he is often tasked with going for optimal for a given budget, goal, and set of constraints.

 

Haven't all of these points been made over and over? I'm not saying they aren't true, just repeated?