Why top mount?

[Schister66]

I've said it before...EVERYTHING was the same. The same tuner, the same gear, the same setup, the same timing even....the ONLY difference was the manifold.

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[mike@synapse motorsport]

Originally Posted by Schister66

Tony, i was disappointed with the slow spool on the topmount, but i assure you that i ONLY switched from a topmount to a SLS Shorty before that comparison. I dont think the spool times are very accurate on that dyno because my current setup spools at ~3800rpm on the street, but was spooling at 4600rpm on the dyno. I dont understand the large discrepensies...i'm just reporting what happened in my instance.

The turbo for both dynos was my GT3255b. The first manifold, the topmount, was a CoreyR topmount. My current manifold is the SLS shorty. Everything else in the setup was left as is....

either that manifold was total crap which is unlikely, or there was an unseen issue with another part of the top mount setup. fire ring missing, boost leak etc...

i honestly dont think a manifold change can make that much of a difference. i saw 0 difference in spool time and power production from my switch, the graphs were pretty much on top of each other. maybe tomorrow if i get some ill post up a graph of my comparisons. even on a top mount it should have spooled that turbo much faster.

[Chris Tune]

Originally Posted by mike@synapse motorsport

either that manifold was total crap which is unlikely, or there was an unseen issue with another part of the top mount setup. fire ring missing, boost leak etc...

i honestly dont think a manifold change can make that much of a difference. i saw 0 difference in spool time and power production from my switch, the graphs were pretty much on top of each other. maybe tomorrow if i get some ill post up a graph of my comparisons. even on a top mount it should have spooled that turbo much faster.

i x2 x3 everyone on this... something else was wrong between the changes...

have made the change myself and never had that spectacular difference... but oh well... sometimes sh!t happens

[gogunkergorilla]

Seems plausible to me. Some of the difference could be conditions such air temp, humidity, coolant temp, oil temp that were not the same in both tests. I'm not surprised though that the short runners spooled a little faster than the runners three times longer. That extra spool yielded gains through the whole powerband.

I still have yet to hear a credible argument of the performance gain of a top mount vs. another type of equal length manifold.

[ls1_datsun]

A turbo isn't going to make more power because its a topmount, trunk mount or under the dashboard...it doesn't care where it is. Header design is the only thing that matters at the end of the day.

[SPCBoyles]

Originally Posted by ls1_datsun

A turbo isn't going to make more power because its a topmount, trunk mount or under the dashboard...it doesn't care where it is. Header design is the only thing that matters at the end of the day.

huh? Weren't we talking about different "header" designs already?

[ls1_datsun]

Originally Posted by SPCBoyles

huh? Weren't we talking about different "header" designs already?

Too many people generalize things like:

log<mini ram<ramhorn<topmount

that has no meaning thats all im saying

[SPCBoyles]

aah....So you're saying the quality of design of the particular manifold, reguardless of the style, is what matters (I think).

[Archidictus]

Originally Posted by ls1_datsun

Too many people generalize things like:

log<mini ram<ramhorn<topmount

that has no meaning thats all im saying

You are 100%, completely and totally incorrect. Just like in an NA header, the primary runner length and diameter, the quality and precision with which the collector is implemented and the efficiency of flow are the main characteristics in determining the shape and peak of the power curve with a turbo.

That said, however, there are very few street setups I've seen, worked on or heard of that need anything more than a basic log with good wastegate placement. Unless you're gunning for more than 350whp, it shouldn't matter nearly as much as everyone seems to think it does. A bigger downpipe and exhaust will make more of a difference in a street setup than going from a $170 eBay log to a $1200 Full Race ramhorn at 12psi. I've seen it

[ls1_datsun]

Originally Posted by Archidictus

You are 100%, completely and totally incorrect. Just like in an NA header, the primary runner length and diameter, the quality and precision with which the collector is implemented and the efficiency of flow are the main characteristics in determining the shape and peak of the power curve with a turbo.

That said, however, there are very few street setups I've seen, worked on or heard of that need anything more than a basic log with good wastegate placement. Unless you're gunning for more than 350whp, it shouldn't matter nearly as much as everyone seems to think it does. A bigger downpipe and exhaust will make more of a difference in a street setup than going from a $170 eBay log to a $1200 Full Race ramhorn at 12psi. I've seen it

ok i guess you've been around more setups than me...

All im saying is that the key elements in designing a manifold have nothing to do with whether the turbo is up top, down low, etc, etc etc.

You are 100% incorrect if you think there is no difference in a log to a well designed turbo manifold in "street" setups. ..

[Boner_Ben]

I've made 780whp on my 250 dollar used inlinepro t4 log manifold.

[ls1_datsun]

Originally Posted by Boner_Ben

I've made 780whp on my 250 dollar used inlinepro t4 log manifold.

I wouldn't consider an inline pro a "log" manifold..

[Boner_Ben]

Originally Posted by ls1_datsun

I wouldn't consider an inline pro a "log" manifold..

If thats not a log manifold than what is?

[ls1_datsun]

Originally Posted by Boner_Ben

If thats not a log manifold than what is?

A log manifold cylinders 1&4 fire directly into each other and 2&3 into that. Inline pro manifold has an actual merge...

[SPCBoyles]

Originally Posted by ls1_datsun

A log manifold cylinders 1&4 fire directly into each other and 2&3 into that. Inline pro manifold has an actual merge...

I disagree. Ram horn style manifolds are tubular runners routed to a collector. The inline pro is cast stainless steel and there is no collector. It does have "runners", sort of, but "log style" is the closest description you could use for that manifold. Then again, I'm certainly no expert.

[RCautoworks]

Originally Posted by SPCBoyles

I disagree. Ram horn style manifolds are tubular runners routed to a collector. The inline pro is cast stainless steel and there is no collector. It does have "runners", sort of, but "log style" is the closest description you could use for that manifold. Then again, I'm certainly no expert.

Its not a log, rather just a cast turbo manifold... thats what I would call it.

Originally Posted by ls1_datsun

A log manifold cylinders 1&4 fire directly into each other and 2&3 into that. Inline pro manifold has an actual merge...

Get Tony in here, he loves those dam logs

[SPCBoyles]

Well we're kind of getting off subject, reguardless of what that mani is called. By the way, RCautoworks, from what I've seen your manifolds are

[HiProfile]

Originally Posted by ls1_datsun

You are 100% incorrect if you think there is no difference in a log to a well designed turbo manifold in "street" setups. ..

And he's not incorrect - because he's saying he's never seen a street setup that NEEDED a "well designed turbo manifold". People here have shown logs can make MUCH more power than any FWD car can use with street tires. He's also saying an exhaust can do more for making power than a manifold can - and he's right. Look at all the factory turbo forums. A full stainless dp/exhaust costs as much in most cases as a NEW TURBO, yet they upgrade the exhaust first. Subies can do 10's on street tires with a 'bad' manifold - the stock setup pairs the cylinders incorrectly, in terms of interfering exhaust pulses.

BTW the coolest cast mani I've seen is the Greddy/HKS manifold design - it flows like the ssauto mani does, except you're stuck with a T25 flange.

BTW2 I'd guess it was more of an exhaust leak, such as a warped flange. That would explain the slower spool, as well as the slightly reduced power curve everywhere.

[91jdmhatchback]

well i will tell you i have seen/worked on/ fixed things on schiters66's car. i can tell you all he did was switch manifolds/dp/dt and went and had it tuned ... THATS IT.

the topmount that was on his car was a cc-fab product and it wasn't that bad besides the wastgate falling off. now i think he just had a bad combo with a long runner manifold and a smallish turbo. and when he switch to a short runner manifold along with his smallish turbo, it just works better in that combination.

[gogunkergorilla]

Originally Posted by 91jdmhatchback

well i will tell you i have seen/worked on/ fixed things on schiters66's car. i can tell you all he did was switch manifolds/dp/dt and went and had it tuned ... THATS IT.

the topmount that was on his car was a cc-fab product and it wasn't that bad besides the wastgate falling off. now i think he just had a bad combo with a long runner manifold and a smallish turbo. and when he switch to a short runner manifold along with his smallish turbo, it just works better in that combination.

More misconceptions. You do not match runner lengths with turbos. A good rule of thumb that will optimize any turbo setup is to use a manifold with the shortest and straightest runners possible without compromising wastegate placement or downpipe efficiency. Long runners are detrimental if those conditions can be met otherwise.

[91jdmhatchback]

Originally Posted by gogunkergorilla

More misconceptions. You do not match runner lengths with turbos. A good rule of thumb that will optimize any turbo setup is to use a manifold with the shortest and straightest runners possible without compromising wastegate placement or downpipe efficiency. Long runners are detrimental if those conditions can be met otherwise.

so you just said the more complicated version of what i said.

[SPCBoyles]

Originally Posted by 91jdmhatchback

so you just said the more complicated version of what i said.

I don't know if it was even any more complicated. It was almost verbatim.

Anyway...so far the only person in this thread that has shown any kind of PROOF to support his theory is Schister66. Everyone else has stated their opinions on the matter, but shown absolutely no evidence to support it. There will apparently be no concession to the top mount having ANY sort of advantage over other manifold styles. It still seems that, in theory, it has advantages over the other manifolds. These theories make all kinds of sense, but with no data to prove these theories to be true, one can only assume that they are total .

[Schister66]

Lets try to keep this discussion professional...

[SPCBoyles]

hahaha...if I had a fraction of a penny for every unproffessional comment on Honda-Tech, I'd be filthy rich! But I'll try. to me

[high_revs]

great very informative thread